US20070042954A1

US20070042954A1 - Compositions and methods related to soluble G-protein coupled receptors (sGPCRs)

Info

Publication number: US20070042954A1
Application number: US11/350,411
Authority: US
Inventors: Alon Chen; Marilyn Perrin; Wylie Vale
Original assignee: Research Development Foundation
Current assignee: Research Development Foundation
Priority date: 2005-02-08
Filing date: 2006-02-08
Publication date: 2007-02-22
Also published as: US8258279B2; AU2006212813A1; ATE540970T1; US20090117649A1; JP4859248B2; RU2423378C2; RU2007133648A; WO2006086402A3; JP2008529500A; KR20070112155A; CA2597065A1; DK1885746T3; AU2006212813B2; CN101137668A; CN101137668B; EP1885746A2; US7507794B2; CA2597065C; WO2006086402A2; EP1885746B1

Abstract

The present invention is directed to compositions and methods related to soluble G-protein coupled receptors (sGPCR). In ceratin aspects the invention includes compositions and methods related to a soluble corticotropin releasing factor receptor related protein, sCRFR2, as well as its effects on CRFR signaling and interaction between CRF family ligand and CRFR receptors, including but not limited to CRFR2, CRFR1 and functional or signaling capable variants thereof.

Description

This application claims priority to provisional U.S. Patent Application No. 60/650,866, filed Feb. 8, 2005, which is incorporated herein by reference in its entirety.
The United States Government owns rights in present invention pursuant to grant number DK 26741 from the NIDDK.

I. TECHNICAL FIELD

The present invention is directed generally to method and compositions related to molecular biology, neurology, and endocrinology. In certain aspects it is directed to compositions comprising and methods of using soluble G-protein coupled receptors (sGPCRs) as modulators of GPCR activity and/or modulators of the pharmacologic effects of the ligands that bind such soluble GPCRs.

II. BACKGROUND OF THE INVENTION

Receptors, in general, are molecular structures located in the cell membrane or within a cell that form a weak, reversible bond with an agent such as an antigen, hormone, or neurotransmitter. Each receptor is designed to bind with a specific agent(s). A specific family of receptors is the seven transmembrane (“7TM”) or G-Protein-Coupled Receptor (“GPCR”). These receptors link with a Guanine Nucleotide-Binding G-protein (“G-protein”) in order to signal when an appropriate agent has bound the receptor. When the G-protein binds with Guanine DiPhosphate (“GDP”), the G-protein is inactive, or in an “off position.” Likewise, when the G-protein binds with Guanine TriPhosphate (“GTP”), the G-protein is active, or in an “on position” whereby activation of a biological response in a cell is mediated.
GPCRs share a common structural motif. All these receptors have seven sequences of between 22 to 24 hydrophobic amino acids that form seven alpha helices, each of which spans the membrane (i.e., transmembrane-1 (TM-1), transmebrane-2 (TM-2), etc.). The transmembrane helices are joined by strands of amino acids between transmembrane-2 and transmembrane-3, transmembrane-4 and transmembrane-5, and transmembrane-6 and transmembrane-7 on the exterior, or “extracellular” side, of the cell membrane (these are referred to as “extracellualr loops” or “extracellular” regions). The transmembrane helices are also joined by strands of amino acids between transmembrane-1 and transmembrane-2, transmembrane-3 and transmembrane-4, and transmembrane-5 and transmembrane-6 on the interior, or “intracellular” side, of the cell membrane (these are referred to as “intracellular loops” or “intracellular” regions). The “carboxy” (“C”) terminus of the receptor lies in the intracellular space within the cell, and the “amino” (“N”) terminus of the receptor lies in the extracellular space outside of the cell.
Generally, when a ligand binds with the receptor and “activates” the receptor, there is a change in the conformation of the intracellular region that allows for coupling between the intracellular region and an intracellular “G-protein.” It has been reported that GPCRs are “promiscuous” with respect to G-proteins, i.e., that a GPCR can interact with more than one G-protein (Kenakin, 1988). Although other G-proteins exist, currently, Gq, Gs, Gi, and Go are G-proteins that have been identified. Ligand-activated GPCR coupling with the G-protein begins a signaling cascade process or signal transduction. Under normal conditions, signal transduction ultimately results in cellular activation or cellular inhibition. It is thought that the third intracellular loop (IC-3) as well as the carboxy terminus of the receptor interact with the G-protein.
In general, the activity of almost every cell in the body is regulated by extracellular signals. A number of physiological events in humans as well as with a wide range of organisms use protein mediated transmembrane signaling via GPCRs. Signals from a specific GPCR cause activation of a G-protein in the cell. The majority of signals are transmitted by means of GPCRs into the cell interior. There are many varying aspects of this signaling process involving multiple receptor subtypes for GPCRs and their G-protein linked counterparts as well as a variety of linked intracellular secondary messengers. The signal transduction may result in an overall or partial activation or inactivation of an intracellular process or processes depending upon the proteins that are involved. Important signaling molecules or neurotransmitters which bind to GPCRs include, but are not limited to corticotropin releasing factor, parathyroid hormone, morphine, dopamine, histamine, 5-hydroxytrytamine, adenosine, calcitonin, gastric inhibitory peptide (GIP), glucagon, growth hormone-releasing hormone (GHRH), parathyroid hormone (PTH), PACAP, secretin, vasoactive intestinal polypeptide (VIP), diuretic hormone, EMR1, latrophilin, brain-specific angiogenesis inhibitor (BAI), cadherin, EGF, LAG, (CELSR), and other similar proteins or molecules.
GPCRs constitute a superfamily of proteins. There are currently over 2000 GPCRs reported in literature, which are divided into at least three families: rhodopsin-like family (family A), the calcitonin receptors (family B), and metabotropic glutamate family (family C) (Ji et al., 1998). The reported GPCRs include both characterized receptors and orphan receptors for which ligands have not yet been identified. (Wilson et al., 1999; Wilson et al., 1998; Marchese et al., 1999). Despite the large number of GPCRs, generally, each GPCR share a similar molecular structure. Each GPCR comprises a string of amino acid residues of various lengths. GPCRs lie within the cell membrane in seven distinct coils called transmembranes. The amino terminus of the GPCR lies outside the cell with the extracellular loops, while the carboxy-terminus lies inside the cell with the intracellular loops.
The ligands for GPCRs comprise small molecules as well as peptides and small proteins. The interactions between these ligands and their receptors vary from system to system but they may require the interaction with residues in several of the four extracellular domains and the N-terminus. In some instances the N-terminus alone may maintain an ability to interact with or bind ligands. GPCRs with known ligands have been associated with many diseases including multiple sclerosis, diabetes, rheumatoid arthritis, asthma, allergies, inflammatory bowel disease, several cancers, thyroid disorders, heart disease, retinitis pigmentosa, obesity, neurological disorders, osteoporosis, Human Immunodeficiency Virus (“HIV”) infection and Acquired Immune Deficiency Syndrome (“AIDS”) (Murphy et al., 2000; Mannstadt et al., 1999; Berger et al., 1999; Jacobson et al., 1997; Meij, 1996;).
Accordingly, there is a need in the art for methods of producing modulators of GPCRs and the ligands that bind GPCRs for use as therapeutics. These therapeutics may be used to prevent or treat GPCR associated diseases and/or disorders.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to compositions and methods related to a sGPCR ligand binding domains, as well as effects of the sGPCR on GPCR signaling and interaction between GPCR ligands and their GPCRs.
An embodiment of the invention includes an isolated soluble G-protein coupled receptor (sGPCR) ligand binding domain. A sGPCR comprises all or part of a GPCR extracellular domain. In one aspect of the invention the sGPCR is an soluble form of a GPCR family B member. In a further apsect the sGPCR is a GPCR subfamily B1 member. In still further aspects, a sGPCR is a soluble secretin receptor, VPAC₁receptor, VPAC₂receptor, PAC₁receptor, glucagon receptor, growth hormone releasing hormone (GHRH) receptor, glucagon-related peptide 1 (GLP-1) receptor, glucagon-related peptide 2 (GLP-2) receptor, gastric inhibitory polypeptide (GIP) receptor, corticotropin releasing factor 1 (CRF1) receptor, cortisotropin releasing factor 2 (CRF2) receptor, parathyroid hormone 1 (PTH1) receptor, parathyroid hormone 2 (PTH2) receptor, calcitonin receptor-like receptor, or calcitoinin receptor. The sGPCR can be a soluble PTH1 receptor or PTH2 receptor. An embodiment of the invention also includes a sGPCR that is a soluble form of the corticotropin releasing factor receptor type 2α (sCRFR2α). The amino acid sequence of a sCRFR2α may comprise an amino acid sequence encoded by exons 3, 4, and 5 of the CRFR2α gene or does not contain exon 6 or greater. A recombinant sGPCR of the invention may include 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 130, 135, 140, 150, 155, 160, 180, 200 or more amino acids, including all ranges there between, of an GPCR extracellular domain(s), including all or part of the amino terminal extracellular domain. In certain apsects, a sGPCR ligand binding domain may comprise an amino acid sequence at least 70, 75, 80, 85, 90, 95, or 98% similar to 50, 75, 100, 125, 150 or more amino acids of SEQ ID NO:4 (sCRFR2α), SEQ ID NO:8 (sCRFR2β), SEQ ID NO:12 (sCRFR2γ), or SEQ ID NO:15 (mCRFR2α). In a further aspect, a sCRFR comprises the amino acid sequence of SEQ ID NO:4, 8, 12, 15 or a combination thereof. In a still further aspect, the invention includes an isolated sGPCR further comprising an affinity tag, a label, a detectable or therapeutic chemical moiety, a biotin/avidin label, a radionuclide, a detectable or therapeutic enzyme, a fluorescent marker, a chemiluminescent marker, an immunoglobulin domain or any combination thereof. In one asepct, the GPCR comprises an immunoglobulin domain, in particular an Fc domain. The sGPCR can be conjugated to a polymer, which includes, but is not limited to polyethylene glycol (PEG).
Embodiments of the invention include polynucleotides encoding sGPCR of the invention. Polynucleotide may further comprise a promoter operably coupled to the polynucleotide encoding the sGPCR. The sGPCR encoding sequence can be included in an expression cassette. The expression cassette may be comprised in an expression vector. The expression vector may include, but is not limited to a linear nucleic acid, a plasmid expression vector, or a viral expression vector. In certain aspects, an expression vector is comprised in a delivery vector, which may include, but is not limited to a liposome, a polypeptide, a polycation, a lipid, a bacterium, or a virus.
Still further embodiments of the invention include methods of modulating the activity of G-protien coupled receptor (GPCR) comprising: a) contacting a target tissue with a sGPCR; and b) binding a GPCR ligand in the vicinity of the target tissue, wherein the activity of the GPCR in the tissue is modulated. The ligand can be a GPCR family B ligand, a GPCR subfamily B1 ligand. In certain aspects the ligand is a corticotropin releasing factor (CRF), urocortin 1, urocortin 2, usorcortin 3, stresscopin, parathyroid hormone, PTH-related hormone, TIP39, calcitonin, amylin, CGRP (CALCA and CALCB), adrenomedullin, secretin, VIP, PACAP, glucagon, GHRH, GLP-1, GLP-2, GIP or any combination thereof. The methods may also include contacting a target tissue comprising the steps of: a) preparing sGPCR ligand binding domain in an apprpriate pharmaceutical solution; and b) adminstering the pharmaceutical solution to an animal, human, subject, and/or patient in an amount to affect binding of a target ligand in the target tissue of the animal. Administration can be, but is not limited to ingestion, injection, endoscopy or perfusion. Injection includes, but is not limited to intravenous, intramuscular, subcutaneous, intradermal, intracranial or intraperitoneal injection. Disorders that may be treated, ameliorated, modulation, reduced in severity, include disorders resulting from hyperactivation of a GPCR or hypersecretion of GPCR ligand. In certain aspects the disorder is insulin sensitivity or type II diabetes. The disorder may also include an anxiety-related disorder; a mood disorder; a post-traumatic stress disorder; supranuclear palsy; immune suppression; drug or alcohol withdrawal symptoms; inflammatory disorders; pain; asthma; psoriasis and allergies; phobias; sleep disorders induced by stress; fibromyalgia; dysthemia; bipolar disorders; cyclothymia; fatigue syndrome; stress-induced headache; cancer; human immunodeficiency virus infections; neurodegenerative diseases; gastrointestinal diseases; eating disorders; hemorrhagic stress; stress-induced psychotic episodes; euthyroid sick syndrome; syndrome of inappropriate antidiarrhetic hormone; obesity; infertility; head traumas; spinal cord trauma; ischemic neuronal damage; excitotoxic neuronal damage; epilepsy; cardiovascular and heart related disorders; immune dysfunctions; muscular spasms; urinary incontinence; senile dementia of the Alzheimer's type; multiinfarct dementia; amyotrophic lateral sclerosis; chemical dependencies and addictions; psychosocial dwarfism, insulin hypersensitivity or hyposensitivity, hypoglycemia, skin disorders; or hair loss. In certain aspects the disorder is an anxiety-related disorder; a mood disorder; bipolar disorder; post-traumatic stress disorder; inflammatory disorder; chemical dependency and addiction; gastrointestinal disorder; or skin disorder. In a further aspect the anxiety-related disorder is generalized anxiety or the mood disorder is depression. In still a fruthre aspect the gastrointestinal disorder is irratable bowel syndrome.
Other embodiments of the invention include methods of detecting a GPCR ligand comprising: a) contacting a sample suspected of containing a GPCR ligand with a sGPCR polypeptide; and b) assessing the presence or absence of sGPCR polypeptide bound ligand. The methods may further comprise characterizing the bound ligand. Characterizing a bound ligand includes, but is not limited to various chromatographies, mass spectrometry, peptide sequencing and the like. The sGPCR polypeptide may or may not be operably coupled to a substrate or surface. The method can further comprise: c) adminstering a radiolabled GPCR ligand; and d) assessing binding or competition for binding of the radiolabeled GPCR ligand to the sGPCR. The GPCR ligand may include, but is not limited to corticotropin releasing factor (CRF), urocortin 1, urocortin 2, usorcortin 3, parathyroid hormone, PTH-related hormone, TIP39, calcitonin, amylin, CGRP (CALCA and CALCB), adrenomedullin, secretin, VIP, PACAP, glucagon, GHRH, GLP-1, GLP-2, or GIP.
Still other embodiments include methods of detecting a sGPCR comprising: a) contacting a sample suspected of containing a sGPCR with a ligand that binds the sGPCR or a related surface bound GPCR; and b) assessing binding of GPCR ligand with components of the sample. The method can further comprise characterizing the bound sGPCR, which can include chromatography, mass spectrometry, protein fragmentation and sequencing, and the like. A GPCR ligand may be operably coupled to a substrate or surface. The methods can further compris: c) adminstering a radiolabled sGPCR; and d) assessing binding or competition for binding of the radiolabeled sGPCR to the GPCR ligand in the presence and absence of the sample being tested. Exemplary ligands include corticotropin releasing factor (CRF), urocortin 1, urocortin 2, usorcortin 3, parathyroid hormone, PTH-related hormone, TIP39, calcitonin, amylin, CGRP (CALCA and CALCB), adrenomedullin, secretin, VIP, PACAP, glucagon, GHRH, GLP-1, GLP-2, GIP or other know GPCR ligands.
In yet still another embodiment of the invention includes antibodies that specifically bind a sGPCR. In certain aspects an antibody may bind the amino terminus or carboxy terminus of the sGPCR. Aspects of the invention include an antibody that binds a carboxy terminal 5, 10, 15, 20 or more amino acid sequence, which may be derived from an alternative reading frame of a nucleotide sequenc that encodes a transmembrane region of a GPCR (typically the result of alternative splicing and may be engineered into a recombinant polynucleotide of the invention).
Embodiments of the invention include methods of detecting the expression of a sGPCR, either using protein, nucleic acid or both protein and nucleic acid evaluation or assessment. Aspects of the invention include methods of detecting a sGPCR mRNA comprising: a) obtaining a nucleic acid sample to be analyzed; and b) assessing the presence of a sGPCR nucleic acid comprising a splice junction resulting in a sGPCR. The method may include assessing the presence of a particular species of mRNA by nucleic hybridization, nucleic acid amplification or other methods of analyzing nucleic acids. In a particular aspect a sGPCR is a soluble B type GPCR, a soluble B1 type GPCR, a soluble CRFR, a sCRFR1, a sCRFR2, or a sCRFR2α. A polynucleotide can include an exon/exon junction that includes the amino terminal amino acids of a GPCR and none or part of an exon encoding a portion of a transmembrane domain. In a particular aspect the splice junction of a sCRFR2α is an exon 5/exon 7 junction, wherein exon desigantion is based on the genomic designation of CRFR2 exons. Based on the CRFR2α transcript the exons would be designated 3 and 5, respectively (see FIG. 1 for an example).
A “soluble” GPCR (sGPCR) means a GPCR that comprises all or part of an extracellular domain of a receptor, but lacks all or part of one or more transmembrane domains which normally retains the full length receptor in the cell membrane, the soluble form is not integrated into the cell membrane. Thus, for example, when such a soluble receptor is produced recombinantly in a mammalian cell, it can be secreted frrom the recombinant host cell through the plasma membrane, rather than remaining at the surface of the cell. In general, a soluble receptor of the invention is soluble in an aqueous solution. However, under certain conditions, the receptor can be in the form of an inclusion body, which is readily solubilized by standard procedures. Such sGPCR may be derived from an engneered nucleic acid, a processed protein (e.g., protealized protein), a synthesized protein, or an isolated splice variant. A polynucleitide encoding such a sGPCR may be isolated or engineered.
As used herein, the terms “isolated” and “purified” are used interchangeably to refer to nucleic acids or polypeptides or biologically active portions thereof that are substantially or essentially free from components that normally accompany or interact with the nucleic acid or polypeptide as found in its naturally occurring environment. Thus, an isolated or purified nucleic acid or polypeptide is substantially free of other cellular material or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized.
An “isolated” nucleic acid is free of sequences (preferably protein-encoding sequences) that naturally flank the nucleic acid (i.e., sequences located at the 5′ and 3′ ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is derived. For example, in various embodiments, the isolated nucleic acids can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb, or 0.1 kb of nucleotide sequences that naturally flank the nucleic acids in genomic DNA of the cell from which the nucleic acid is derived.
As used herein, the term “isolated” or “purified” as it is used to refer to a polypeptide of the invention means that the isolated protein is substantially free of cellular material and includes preparations of protein having less than about 30%, 20%, 10%, 5% or less (by dry weight) of contaminating protein. When the protein of the invention or biologically active portion thereof is recombinantly produced, preferably culture medium represents less than about 30%, 20%, 10%, or 5% (by dry weight) of chemical precursors or non-protein-of-interest chemicals.
The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”
The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the matter in which the above-recited features, advantages, and objects of the invention as well as others which will become clear are attained and can be understood in detail, more particular descriptions and certain embodiments of the invention briefly summarized above are illustrated in the appended drawings. These drawings form a part of the specification. It is to be noted, however, that the appended drawings illustrate certain embodiments of the invention and therefore are not to be considered limiting in their scope.
FIGS. 1A-1B. Illustrate an exemplary nucleotide and translated amino acid sequence of a soluble GPCR, the CRF receptor type 2α (sCRFR2α) (FIG. 1A). Underlined amino acids indicate the unique C-terminal tail. Boxed residues indicate putative N-linked glycosylation sites. Schematic representation of the structure of the mouse CRFR2 gene (upper panel), the two known functional transcripts in mouse, α and β (middle panels) and the novel sCRFR2α splice variant (lower panel) (FIG. 1B). The locations of the translation start sites (ATG) are indicated. Exons coding for the N-terminal extracellular domain (ECD), the seven transmembrane domains (7TM), and the C-terminal cytoplasmic domain (CD) are indicated. 5′ and 3′-UTRs are indicated by hatched boxes. Black boxes represent coding regions and open boxes represent exons downstream to the stop codon.
FIGS. 2A-2C. Show expression of CRFR2α and sCRFR2α mRNA in mouse brain and pituitary. FIG. 2A is a schematic representation and the oligonucleotide primer locations of the amplified portion of mouse CRFR2α (upper panel) and sCRFR2α (lower panel) transcripts. The locations of the oligonuleotide primers, at exons three and seven, which result in the amplification of two products of 418 and 309 corresponding to CRFR2α and sCRFR2α, respectively, are indicated. FIG. 2B is a representative image of electrophoretic analysis of the semiquantitative RT-PCR for mCRFR2α and sCRFR2α mRNA and the ribosomal protein S16 mRNA (upper panels). Southern blot hybridization of amplified mCRFR2α and sCRFR2α cDNA and the ribosomal protein S16 cDNA fragments were also performed (lower panels). The radioactive bands were quantified by PhosphorImager and normalized values (relative to the S16 expression) are presented as relative densitometry units (FIG. 2C).
FIGS. 3A-3C. A highly specific antiserum raised in rabbit using a synthetic peptide fragment encoding the unique C-terminal tail of mouse sCRFR2α protein (aa 113-143) was used to develop a sCRFR2α radioimmunoassay, used for immunoblot analysis and for immunocytochemistry. FIG. 3A is a western immunoblot of mouse sCRFR2α isolated from the medium of COS-M6 cells transiently transfected with sCRFR2αFLAG construct reacted with anti-sCRFR2α-(113-143) serum (left panel) or monoclonal M2 anti-FLAG (right panel). Lanes 1, 2, and 3 correspond to 0.1, 1.0, and 10 μl of sCRFR2α-FLAG extract, respectively. FIG. 3B, Displacement of [¹²⁵I]Tyr¹¹³sCRFR2α (aa 113-143) binding to rabbit anti-sCRFR2α (aa113-143) by synthetic sCRFR2α (aa 113-143) and by purified COS-M6 expressed sCRFR2α (aa 113-143)-FLAG. FIG. 3C, Immunofluorescence staining of COS-M6 cells transiently transfected with mouse sCRFR2α construct visualized with the anti-sCRFR2α (aa 113-143) serum followed by a Cy3-conjugated secondary antibody (FIG. 3C(b)). The slides were counterstained with DAPI to visualize both transfected and non transfected cells (FIG. 3C(a)). Cells incubated with normal rabbit serum (NRS), as negative control, followed by a Cy3-conjugated secondary antibody did not show any staining (FIG. 3C(c)).
FIGS. 4A-4G. Illustrates the presence of sCRFR2α-like immunoreactivity (ir) in the mouse brain using immunohistochemistry and radioimmunoassay (RIA). FIGS. 4A-4F show immunoperoxidase staining for sCRFR2α in select mouse brain regions. Major sites of cellular expression included the principal output neurons of the olfactory bulb (FIG. 4A); the medial septal nucleus (FIG. 4B); and the basolateral (BLA), but not the central (CeA) nucleus of the amygdala (FIG. 4C); cerebral cortex, where stained cells were localized mainly in layers 5 and 2/3 (FIG. 4D); and red nucleus (FIG. 4E). In each of these sites, the pattern of cellular labeling was similar, though not necessarily identical, to that of CRFR1 mRNA expression. Immunolabeled fibers and varicosities were restricted to a handful of cell groups, including the paraventricular nucleus of the hypothalamus (PVH; FIG. 4F). FIG. 4G, sCRFR2α-like immunoreactivity in acid-extracted and partially purified tissue isolated from mouse brain was measured by radioimmunoassay. Tissue extracts were tested at 5-7 dose levels and displaced [¹²⁵I]-labeled Tyr¹¹³sCRFR2α (aa 113-143) binding to rabbit anti-sCRFR2α (aa 113-143) in a dose-dependent manner.
FIGS. 5A-5B. sCRFR2α protein interferes with the induction of cAMP and MAPK signaling mediated by Ucn 1 or CRF. FIG. 5A shows activation of CRE-luciferase reporter by Ucn 1 or CRF, with or without sCRFR2α preincubation, in 293T cells transiently transfected with mouse CRFR2α. Luciferase reporter containing a fragment of the CRE promoter of the EVX1 gene was cotransfected into 293T cells with CRFR2α expression vectors. Luciferase activity was measured following treatment (4 h) with 0.0001-100 nM Ucn 1 or CRF, in the presence or absence of 0.1 nM sCRFR2α. Assays were normalized to cotransfected β-galactosidase activity. The representative means of six replicates from one experiment is shown in the graph. FIG. 5B, Equilibrated CATH.a cells were treated with Ucn 1 (10 nM) with or without sCRFR2α (0.4 or 4 nM). After 5 min of receptor stimulation, cell lysates were harvested and subjected to SDS-PAGE immunoblot analysis using phospho-ERK1/2-p42,44 antibody and ERK2-p44 antibody. The ERK activation was calculated by normalizing the levels of phosphorylated ERK1/2-p42,44 to total ERK2-p44. The representative of means of triplicates from one experiment is shown in the graph. *, P<0.05 vs. vehicle treatment, #, P<0.05 vs. Ucn 1 treatment, UD=undetected.

DETAILED DESCRIPTION OF THE INVENTION

Useful therapeutic approaches for the treatment of diseases associated with GPCRs and associated signalling pathways include the inhibition or modulation of the activation or inhibition of the GPCR. One approach is the development of small molecule inhibitors, which are costly to develop and bring to market. A drawback of the treatment with small molecule inhibitors or antagonists of GPCRs is the risk of toxicity, particularly with repeated application. Also, many GPCRs have no small molecule receptor antagonists. The development of a GPCR anatagonist that is less costly and/or less toxic than small molecule inhibitors is worthwhile. Embodiments of the invention are directed to compositions and methods related to soluble GPCR (sGPCR) ligand binding domains, as well as its effects on GPCR signaling and interaction between GPCR ligands and their GPCRs. sGPCRs may be used to antagonize the activation or inhibition of GPCRs in vitro and/or in vivo.
I. G-Protein Couples Receptors (GPCRs)
GPCRs constitute a superfamily of proteins, which are divided into three families: rhodopsin-like family (family A), the calcitonin receptors (family B), and metabotropic glutamate family (family C) (Ji et al., 1998), each of which may further be divided into subfamilies. The reported GPCRs include both characterized receptors and orphan receptors, those for which ligands have not yet been identified (Wilson et al., 1999; Wilson et al., 1998; Marchese et al., 1999). Despite the large number of GPCRs, generally, each GPCR share a similar molecular structure. Each GPCR comprises a string of amino acid residues of various lengths. GPCRs lie within the cell membrane in seven distinct coils called transmembranes. The amino terminus of the GPCR is outside the cell as are the extracellular loops, while the carboxy-terminus is inside the cell with the intracellular loops.
GPCR family A (Rhodopsin like) includes, but is not limited to amine, peptide, hormone protein, rhodopsin, olfactory, prostanoid, nucleotide-like, cannabinoid, platelet activating factor, gonadotropin-releasing hormone, thyrotropin-releasing hormone and secretagogue, melatonin, viral, lysosphingolipid and LPA (EDG), leukotriene B4 receptor and other similar receptor proteins.
GPCR family B (Secretin like) includes, but is not limited to receptors for calcitonin, corticotropin releasing factor (CRF), gastric inhibitory peptide (GIP), glucagon, growth hormone-releasing hormone (GHRH), parathyroid hormone (PTH), pituitary adenylate cyclase-activating polypeptide (PACAP), secretin, vasoactive intestinal polypeptide (VIP), diuretic hormone, EMR1, latrophilin, brain-specific angiogenesis inhibitor (BAI), methuselah-like proteins (MTH), cadherin/EGF/LAG (CELSR), and other similar ligands. Harmar (2001) describes three subfamilies of GPCR family B, subfamily B1, B2 and B3.
Subfamily B1—Subfamily B1 includes, but is not limited to the classical hormone receptors, which are encoded by at least 15 genes in humans, with at least five putative members in Drosophila and three in C. elegans. The ligands for receptors in this family are polypeptide hormones of approximately 27-141 amino-acid residues; at least nine of the mammalian receptors respond to ligands that are structurally related to one another (glucagon, glucagon-like peptides (GLP-1, GLP-2), glucose-dependent insulinotropic polypeptide, secretin, vasoactive intestinal peptide (VIP), PACAP, and growth-hormone-releasing hormone (GHRH). All members of this subfamily have been shown to be capable of regulating intracellular concentrations of cAMP by coupling to adenylate cyclase through a stimulatory G protein (Gs). Some members of the subfamily are capable of signaling through additional G-protein-coupled signaling pathways, for example through activation of phospholipase C.
Subfamily B2—Subfamily B2 consists of a large number of family-B GPCRs with long extracellular amino termini, containing diverse structural elements linked to the core 7TM motif. The prototype members of this subfamily were an EGF-module-containing, mucin-like hormone receptor (EMR1) isolated from a human neuroectodermal cDNA library (Baud et al., 1995) and the leukocyte cell-surface antigen CD97 (Hamann et al., 1995). Subfamily B2 also includes the calcium-independent receptors for α-latrotoxin. Three genes encoding calcium-independent latrotoxin receptors (CL-1 CL-2 and CL-3) have been identified. Secondly, the brain- specific angiogenesis inhibitors 1, 2 and 3 (BAI1, BAI2, BAI3), a group of proteins that have been implicated in the vascularization of glioblastomas are also included in this subfamily. Thirdly, the protein encoded by the Drosophila gene flamingo and its orthologs in humans (the cadherin EGF LAG seven-pass G-type receptors Celsr1, Celsr2 and Celsr3) and in C. elegans (F15B9.7) is also included in the B2 subfamily. Finally, the subfamily includes a fourth, diverse group of receptors that contain some motifs common to receptors in subfamily B2 but are otherwise structurally unrelated (human epididymis 6 (HE6), EGF-TM7-latrophilin-related protein (ETL), the immunoglobulin-repeat-containing receptor Ig hepta, G-protein-coupled receptor 56 (GPR56) and very large G-protein-coupled receptor 1 (VLGR1)). Analysis of the sequenced human genome (1 Apr. 2001, UCSC Human Genome Project Working Draft (genome.ucsc.edu)) indicates that there are at least 18 human genes encoding members of subfamily B2, and there are at least four in Drosophila and three in C. elegans. The structure and functions of members of subfamily B2 have been reviewed recently by Stacey et al. (2000).
Subfamily B3—The prototype of a third group (subfamily B3) of family-B GPCRs is methuselah (mth), a gene isolated in a screen for single-gene mutations that extended average lifespan in D. melanogaster (Lin et al., 1998). The gene encodes a polypeptide that displays sequence similarity to other family-B GPCRs solely within the TM7 region. A least eight paralogs of methuselah are encoded within the Drosophila genome sequence.
The characteristic feature of all family-B GPCRs is the 7TM motif, which is distantly related to comparable regions of some other GPCR families but much more highly conserved within family B. Conserved cysteine residues within extracellular loops EC1 and EC2 probably form a disulphide bridge, by analogy with family-A GPCRs in which this feature is also conserved (Palczewski et al., 2000). In contrast to family-A GPCRs, however, many of which appear to rely on internal hydrophobic sequences for targeting to the plasma membrane, most family-B GPCRs appear to have an amino-terminal signal peptide. Studies using site-directed mutagenesis and the construction of chimeras between hormone receptors in family B have shown that the amino-terminal extracellular domain is essential for ligand binding but that the transmembrane domains and associated extracellular loop regions of the receptors provide information necessary for specific interaction with ligands. All of the hormone receptors in family B contain a conserved region within the amino-terminal extracellular domain close to TM1 that may play a role in ligand binding. Splice variation in this region of the PAC1 receptor has been shown to influence ligand-binding specificity and affinity (Dautzenberg et al., 1999).
Receptors in subfamily B2 contain a variety of additional structural motifs in their large amino-terminal extracellular domains that suggest a role for this domain in cell-cell adhesion and signaling. These include EGF domains (in Celsr1, Celsr2, Celsr3, EMR1, EMR2, EMR3, CD97 and Flamingo), laminin and cadherin repeats (in Flamingo and its human orthologs Celsr1, Celsr2 and Celsr3), olfactomedin-like domains (in the latrotoxin receptors), thrombospondin type 1 repeats (in BAI1, BAI2 and BAI3) and, in Ig hepta, an immunoglobulin C-2-type domain also found in fibroblast growth factor (FGF) receptor 2 and in the neural cell adhesion molecule L1. VLGR1 has two copies of a motif (Calx-beta) present in Na+-Ca2+exchangers and integrin subunit β4.
Family C (Metabotropic glutamate/pheromone) GPCR includes Metabotropic glutamate, calcium-sensing like, putative pheromone receptors, GABA-B, orphan GPRC5, orphan GPCR6, bride of sevenless proteins (BOSS), taste receptors (T1R) and other similar proteins.

In certain embodiments, the sGPCRs of the invention are class B receptors. In aspect, the sGPCRs of the invention are subfamily B1 receptors, and in a further aspect, the sGCPRs are CRFR1 and CRFR2, and parathyroid hormone receptor. Table 1 includes a non-limiting set of exemplary members of the GPCR family, accession numbers and associated UNIGENE and OMIM entries are incorporated herein by reference as of the priority date and the date of filing of this application. Unigene entries can be accessed by internet links contained in OMIM webpage. Numerous other GPCRs and their accession numbers may be found at the website defined by the following address on the world wide web gpcr.org/7tm/htmls/entries.html.

TABLE 1


Exemplary GPCRs.

	Protein acc. #/mRNA ace #/
	OMIM # (each of which are
GPCR description	incorporated by reference)

BRAIN-SPECIFIC ANGIOGENESIS INHIBITOR 1 (BAI 1)	O14514/AB005297/602682
BRAIN-SPECIFIC ANGIOGENESIS INHIBITOR 2 (BAI 2)	O60241/CR623649/602683
BRAIN-SPECIFIC ANGIOGENESIS INHIBITOR 3 (KIAA0550a)(BAI 3)	O60242/AB005299/602684
CALCITONIN RECEPTOR (CT-R, CALCR)	P30988/NM_001742/114131
LEUCOCYTE ANTIGEN CD97	P48960/X84700/601211
CALCITONIN GENE-RELATED PEPTIDE TYPE 1 RECEPTOR, CGRP	Q16602/NM_005795/114190
TYPE 1 RECEPTOR, CALCRL, CGRPR
CORTICOTROPIN RELEASING FACTOR RECEPTOR 1 (CRF-R, CRF1,	P34998/NM_004382/122561
CRHR1, CRHR, CRFR)
CORTICOTROPIN RELEASING FACTOR RECEPTOR 2 (CRF-R, CRF2,	Q13324/NM_001883/602034
CRHR2, CRF2R, CRH2R)
CELL SURFACE GLYCOPROTEIN EMR1 (EMR1 HORMONE	Q14246/X81479/600493
RECEPTOR)
EGF-LIKE MODULE EMR2	AAF21974/AF114491/606100
EGF-LIKE MODULE-CONTAINING MUCIN-LIKE RECEPTOR EMR3	AAK15076/AF239764/606101
GASTRIC INHIBITORY POLYPEPTIDE RECEPTOR (GIP-R, GLUCOSE-	P48546/NM_000164/137241
DEPENDENT INSULINOTROPIC POLYPEPTIDE RECEPTOR)
GLUCAGON-LIKE PEPTIDE 1 RECEPTOR (GLP-1 RECEPTOR, GLP-1-R,	P43220/NM_002062/138032
GLP1R)
GLUCAGON RECEPTOR (GL-R, GCGR)	P47871/NM_000160/138033
GLUCAGON-LIKE PEPTIDE 2 RECEPTOR (GLP-2 RECEPTOR, GLP-2-R,	O95838/NM_004246/603659
GLP-2R, GLP2R)
G PROTEIN-COUPLED RECEPTOR 56	AAD30545/NM_005682/604110
GROWTH HORMONE-RELEASING HORMONE RECEPTOR (GHRH	Q02643/NM_000823/139191
RECEPTOR, GRF RECEPTOR, GRFR, GHRHR)
PITUITARY ADENYLATE CYCLASE ACTIVATING POLYPEPTIDE	P41586/NM_001118/102981
TYPE I RECEPTOR (PACAP TYPE I RECEPTOR, PACAP-R-1,
ADCYAP1R1)
PARATHYROID HORMONE RECEPTOR (PTH2)	P49190/NM_005048/601469
PARATHYROID HORMONE/PARATHYROID HORMONE-RELATED	Q03431/NM_000316/168468
PEPTIDE RECEPTOR (PTHR1)
SECRETIN RECEPTOR (SCT-R, SCTR)	P47872/NM_002980/182098
VASOACTIVE INTESTINAL POLYPEPTIDE RECEPTOR 1 (VIPR1,	P32241/NM_004624/192321
VPAC1)
VASOACTIVE INTESTINAL POLYPEPTIDE RECEPTOR 2 (VIPR2,	P41587/NM_003382/601970
VIP2R, VPAC2, etc.)

A. Corticotropin Releasing Factor (CRF) and its Receptors
As an example of GPCRs contemplated by the invention, the CRF receptors are described in detail. One of skill in the art would be able to adapt these specific teachings to other members of the GPCR family, particularly type B and more particularly to subfamily B1 receptors. In certain aspects the invention includes, but is not limited to the sGPCR derived from the soluble corticotropin releasing factor receptors (sCRFR), in particular sCRFR2α. The hypothalamic hypophysiotropic peptide corticotropin releasing factor (CRF), originally isolated from the hypothalamus (Vale et al., 1981), plays an important role in the regulation of the hypothalamo-pituitary-adrenal (HPA) axis under basal and stress conditions (River and Vale, 1983; Muglia et al., 1995). Further, CRF acts to integrate endocrine, autonomic, and behavioral responses to stressors (River and Vale, 1983; Muglia et al., 1995; Koob and Heinrichs, 1999). The mammalian CRF peptide family comprises urocortin 1 (Ucn 1) (Vaughan et al., 1995) and the peptides, urocortin 2 (Ucn 2) and urocortin 3 (Ucn 3) also known as stresscopin-related peptide (Reyes et al., 2001; Hsu and Hsueh, 2001), and stresscopin (Hsu and Hsueh, 2001; Lewis et al., 2001), respectively.
The effects of CRF-related peptides are mediated through activation of two high affinity membrane receptors, CRFR1 (Chen et al., 1993; Vita et al., 1993; Chang et al., 1993) and CRFR2 (Perrin et al., 1995; Stenzel et al., 1995; Kishimoto et al., 1995; Lovenberg et al., 1995; Chen et al., 2005), which belong to the B1 subfamily of seven-transmembrane domain (7TMD) receptors that signal by coupling to G-proteins. One functional variant of the CRFR1 gene is expressed both in humans and rodents, along with several non-functional variants, which are produced by differential splicing of various exons (Pisarchik and Slominski, 2004; Grammatopoulos et al., 1999). The CRFR2 has three functional splice variants in human (α, β, and γ) and two rodent variants (α and β) that are produced by the use of alternate 5′ exons (Perrin et al., 1995; Stenzel et al., 1995; Kishimoto et al., 1995; Lovenberg et al., 1995; Chen et al., 2005; Grammatopoulos et al., 1999; Kostich et al., 1998). CRFR1 mRNA is widely expressed in mammalian brain and pituitary, with high levels found in the anterior pituitary, cerebral cortex, cerebellum, amygdala, hippocampus, and olfactory bulb (Van Pett et al., 2000). In the periphery, CRFR1 is expressed in testes, ovary, skin, and spleen. CRFR2 mRNA is expressed in a discrete pattern in the brain with highest densities in the lateral septal nucleus (LS), bed nucleus of stria terminalis (BNST), ventromedial hypothalamic nucleus (VMH), olfactory bulb, and mesencephalic raphe nuclei (Van Pett et al., 2000). The CRFR2α is the major splice variant expressed in the rodent brain (Lovenberg et al. 1995) while CRFR2 is expressed in peripheral tissues, with highest levels in the skeletal muscle, heart, and skin (Perrin et al., 1995).
The distributions of CRFR1 and CRFR2 are distinct and imply diverse physiological functions, as demonstrated by the divergent phenotypes of the CRFR1 or CRFR2 null mice. Mice deficient for CRFR1 display decreased anxiety-like behavior and have an impaired stress response (Smith et al., 1998; Timpl et al., 1998), while the CRFR2-null mice have increased anxiety-like behaviors and an exaggerated HPA response to stress (Zhu et al., 1999; Valerio et al., 2001; Khan et al., 1993). However, the responses to administration of CRFR2 agonists and antagonists into specific brain regions reveal both anxiolytic and anxiogenic roles for CRFR2 (Bale and Vale, 2004).
Radioreceptor and functional assays have demonstrated that CRFR1 and CRFR2 differ pharmacologically: Ucn 1 has equal affinities for both receptors and is more potent than CRF on CRFR2, whereas Ucn 2 and Ucn 3 appear to be selective for CRFR2 (Vaughan et al, 1995; Reyes et al., 2001; Lewis et al., 2001). The activation of specific CRFRs in distinct tissues or cell types by receptor-selective CRF peptides initiates a variety of signaling pathways, including coupling to different G-proteins, stimulation of PKB, PKC, intracellular calcium, and mitogen-activated protein kinase (MAPK) (for reviews see Bale and Vale, 2004; Perrin and Vale, 1999; Brar et al., 2002).
CRFR1 and CRFR2 both exist as multiple splice variants. The inventors have identified a cDNA from mouse brain encoding an exemplary splice variant of sCRFR2α in which exon six is deleted from the nucleic acid encoding CRFR2α. Translation of this isoform produces a predicted 143 amino acid soluble protein. The translated protein includes a majority of the first extracellular domain (ECD1) of the CRFR2α followed by a unique 38 amino acid hydrophilic C-terminus resulting from a frame shift produced by deletion of exon six. Studies have demonstrated high levels of expression of sCRFR2α in the olfactory bulb, cortex, and midbrain regions. A protein corresponding to sCRFR2α, expressed and purified from either mammalian or bacterial cell systems, binds several CRF family ligands with low nanomolar affinities. Further, the purified sCRFR2α protein inhibits cellular responses to CRF and urocortin 1. Thus, a sCRFR2α protein can be a biological modulator of CRF family ligands. The modulation of CRF family ligands is not limited to brain and may be used in any tissue that is exposed to one or more members of the CRF family of ligands.
Aspects of the invention generally relate to compositions and methods of achieving a therapeutic effect, including the modulation of GPCR ligand activity, such as CRF family ligands, using a soluble GPCR ligand binding polypeptide, such as CRF binding polypeptide, as an antagonist either alone or together with one or more other hormone antagonist (e.g., small molecule antagonist), including but not limited to antagonist of ligand(s) of the CRF family.
One manner in which to antagonize the action of a ligand is to subject the ligand to a decoy or soluble receptor so as to limit the local concentration of ligand(s) that bind the decoy and modulate the ligands ability to signal via its cell surface receptor. Soluble proteins related to membrane receptors can be generated by enzymatic truncation of membrane bound receptors as suggested for the GHRH receptor (Rekaski et al., 2000), dopamine D3 receptor (Liu et al., 1994), and calcitonin receptor (Seck et al., 2003), or by alternative splicing in the case of the glutamate receptors (Malherbe et al., 1999; Zhu et al., 1999; Valerio et al., 2001). Splice variants containing only the extracellular region of GPCRs have been reported (Pisarchik and Slominski, 2004; Grammatopoulos et al., 1999; Kostich et al., 1998; Malherbe et al., 1999; Zhu et al., 1999; Valerio et al., 2001; Khan et al., 1993; Graves et al., 1992; You et al., 2000; Schwarz et al., 2000). In the majority of cases, these proteins act as binding, non-signaling molecules also referred to as decoy receptors. Two partial cDNA fragments (CRFR1e and CRFR1h), comprising deletion of exon 3 and 4, and addition of a cryptic exon in CRFR1 were identified in human skin and predicted to exist as a soluble proteins (Pisarchik and Slominski, 2004). One of these fragments, CRFR1e, exhibited dominant negative effects when co-transfected with the wildtype CRFR1.
Kehne and Lombaert (2002) disucuss non-peptidic CRF receptor antagonists for the treatment of anxiety, depression, and stress disorders. CRF is implicated in psychiatric disorders, such as anxiety and depression. Since the identification of corticotropin releasing factor (CRF) an extensive research effort has solidified the importance of this 41 amino acid peptide and its related family members in mediating the body's behavioral, endocrine, and autonomic responses to stress.
Preclinical and clinical evidence implicate CRF, in general, and CRF receptors, in particular, in anxiety and depression. Clinical studies have demonstrated a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis and/or elevated CRF levels in depression and in some anxiety disorders. Preclinical data utlilizing correlational methods, genetic models, and exogenous CRF administration techniques in rodents and non-human primates supports a link between hyperactive CRF pathways and anxiogenic and depressive-like symptoms. Studies employing the use of receptor knockouts and selective, non-peptidic antagonists of the CRFR1 have demonstrated anxiolytic and antidepressant effects under certain types of laboratory conditions. A Phase II, open-label, clinical trial in major depressive disorder has reported that a CRFR1 antagonist was safe and effective in reducing symptoms of anxiety and depression.
Various nonlimiting activities of CRF antagonists are described by Owens et al. (1991). CRF antagonists are described as being effective in the treatment of stress-related illnesses; mood disorders such as depression, major depressive disorder, single episode depression, recurrent depression, child abuse induced depression, postpartum depression, dysthemia, bipolar disorders, and cyclothymia; chronic fatigue syndrome; eating disorders such as anorexia and bulimia nervosa; generalized anxiety disorder; panic disorder; phobias; obsessive-compulsive disorder; post-traumatic stress disorder; pain perception such as fibromyalgia; headache; gastrointestinal diseases; hemorrhagic stress; ulcers; stress-induced psychotic episodes; fever; diarrhea; post-operative ileus; colonic hypersensitivity; irritable bowel syndrome; Crohn's disease; spastic colon; inflammatory disorders such as rheumatoid arthritis and osteoarthritis; pain; asthma; psoriasis; allergies; osteoporosis; premature birth; hypertension, congestive heart failure; sleep disorders; neurodegenerative diseases such as Alzheimer's disease, senile dementia of the Alzheimer's type, multiinfarct dementia, Parkinson's disease, and Huntington's disease; head trauma; ischemic neuronal damage; excitotoxic neuronal damage; epilepsy; stroke; spinal cord trauma; psychosocial dwarfism; euthyroid sick syndrome; syndrome of inappropriate antidiuretic hormone; obesity; chemical dependencies and addictions; drug and alcohol withdrawal symptoms; infertility; cancer; muscular spasms; urinary incontinence; hypoglycemia and immune dysfunctions including stress induced immune dysfunctions, immune suppression, and human immunodeficiency virus infections; and stress-induced infections in humans and animals. These and other conditions amenable to CRF modulation are set out in the literature, that includes Lovenberg et al. (1995); Chalmers et al. (1996); and U.S. Pat. No. 5,063,245, each of which is incorporated in its entirety by reference.
II. Polypeptides
Polypeptides of the invention include soluble forms of GPCRs or soluble receptors. Soluble receptors of the invention may comprise subunits which have been changed from a membrane bound to a soluble form. Thus, soluble peptides may be produced by truncating the polypeptide to remove, for example, the 7 transmembrane regions and/or the cytoplasmic tail. Alternatively, the transmembrane domains may be abolished by deletion, or by substitutions of the normally hydrophobic amino acid residues which comprise a transmembrane domain with hydrophilic ones. In either case, a substantially hydrophilic or soluble polypeptide is created which will reduce lipid affinity and improve aqueous solubility. Deletion of the transmembrane domains is preferred over substitution with hydrophilic amino acid residues because it avoids introducing potentially immunogenic epitopes. Soluble receptors of the invention may include any number of well-known leader sequences at the N-terminus. Such a sequence would allow the peptides to be expressed and targeted to the secretion pathway in a eukaryotic system.
A. Fusion Proteins
Receptors are powerful tools to elucidate biological pathways and to treat various disease states via their easy conversion to immunoglobulin fusion proteins. These dimeric soluble receptor forms are good inhibitors of events mediated by either secreted or surface bound ligands. By binding to these ligands they prevent the ligand from interacting with cell associated receptors. Not only are these receptor-Ig fusion proteins useful in an experimental sense, but they have been successfully used clinically in the case of TNF-R-Ig to treat inflammatory bowel disease, rheumatoid arthritis, and the acute clinical syndrome accompanying OKT3 administration (Eason et al., 1996; van Dullemen et al., 1995). The inventors contemplate that manipulation of the many events mediated by signaling through the GPCRs will have wide application in the treatment of GPCR associated diseases.
Preferably, stable plasma proteins—which typically have a half-life greater than hours in the circulation of a mammal—can be used to construct the receptor fusion proteins. Such plasma proteins include but are not limited to: immunoglobulins, serum albumin, lipoproteins, apolipoproteins and transferrin. Sequences that can target the soluble receptors to a particular cell or tissue type may also be attached to the receptor ligand binding domain to create a specifically localized soluble receptor fusion protein.
All or a functional fragment of GPCR extracellular region comprising the GPCR ligand binding domain may be fused to an immunoglobulin constant region like the Fc domain of a human IgG1 heavy chain. Soluble receptor-IgG fusions proteins are common immunological reagents and methods for their construction are well known in the art (see, for example U.S. Pat. No. 5,225,538, which is incorporated herein in its entirety by reference).
A functional GPCR ligand binding domain may be fused to an immunoglobulin (Ig) Fc domain. The Ig Fc may be derived from an immunoglobulin class or subclass including but not limited to IgG1. The Fc domains of antibodies belonging to different Ig classes or subclasses can activate diverse secondary effector functions. Activation occurs when the Fc domain is bound by a cognate Fc receptor. Secondary effector functions include the ability to activate the complement system or to cross the placenta. The properties of the different classes and subclasses of immunoglobulins are described in the art.
One skilled in the art will appreciate that different amino acid residues forming the junction point of the receptor-Ig fusion protein may alter the structure, stability and ultimate biological activity of the sGPCR fusion protein. One or more amino acids may be added to the C-terminus of the selected sGPCR fragment to modify the junction point with the selected fusion domain.
The N-terminus of the sGPCR fusion protein may also be varied by changing the position at which the selected sGPCR DNA fragment is cleaved at its 5′ end for insertion into the recombinant expression vector. The stability and activity of each sGPCR fusion protein may be tested and optimized using routine experimentation, including but not limited to assays for ligand binding.
Using sGPCR ligand binding domain sequences within the extracellular domain as shown herein, amino acid sequence variants may also be constructed to modify the affinity of the sGPCR molecules for their ligands. The soluble molecules of this invention can compete for binding with endogenous receptors. It is envisioned that any soluble molecule comprising a GPCR ligand binding domain that can compete with native receptors for ligand binding is a receptor blocking agent or ligand trapping agent that falls within the scope of the present invention.
B. Protien Conjugates
With respect to the protein's half-life, one way to increase the circulation half-life of a protein is to ensure a reduction in the clearance of the protein, in particular via renal clearance and receptor-mediated clearance. This may be achieved by conjugating the protein to a chemical moiety which is capable of increasing the apparent size, thereby reducing renal clearance and increasing the in vivo half-life. Furthermore, attachment of a chemical moiety to the protein may effectively block proteolytic enzymes from physical contact with the protein, thus preventing degradation by non-specific proteolysis. Polyethylene glycol (PEG) is one such chemical moiety that has been used in the preparation of therapeutic protein products. Recently, G-CSF molecule modified with a single, N-terminally linked 20 kDa PEG group (Neulastam) was approved for sale in the United States. This PEGylated G-CSF molecule has been shown to have an increased half-life compared to non-PEGylated G-CSF and thus may be administered less frequently than current G-CSF products, but it does not reduce the duration of neutropenia significantly compared to non-PEGylated G-CSF.
Polyethylene glycol (PEG) modification is important for pharmaceutical and biotechnological applications. PEGylation (the covalent attachment of PEG) leads for example to shielding of antigenic or immunogenic epitopes. Moreover, it reduces receptor-mediated uptake by the reticuloendothelial system or prevents recognition and degradation by proteolytic enzymes. PEGylation of proteins has been shown to increase their bioavailability by reducing the renal filtration.
The term “conjugate” is intended to indicate a heterogeneous molecule formed by the covalent attachment of one or more polypeptides, typically a single polypeptide, to one or more non-polypeptide moieties such as polymer molecules, lipophilic compounds, carbohydrate moieties or organic derivatizing agents. The term covalent attachment means that the polypeptide and the non-polypeptide moiety are either directly covalently joined to one another, or else are indirectly covalently joined to one another through an intervening moiety or moieties, such as a bridge, spacer, or linkage moiety or moieties. Preferably, the conjugate is soluble at relevant concentrations and conditions, i.e., soluble in physiological fluids such as blood. Compositions and methods for preparing a conjugate of the invention are described in U.S. Pat. No. 6,831,158, which is incorporated herein by reference in its entirety. The methods described in U.S. Pat. No. 6,831,158 are directed to conjugation of G-CSF, but can be readily adapted to conjugation of the sGPCRs of the present invention.
The “polymer molecule” is a molecule formed by covalent linkage of two or more monomers. The term “polymer” may be used interchangeably with the term “polymer molecule”. The term is intended to cover carbohydrate molecules including carbohydrate molecules attached to the polypeptide by in vivo N- or O-glycosylation, such molecule is also referred to as “an oligosaccharide moiety”. Except where the number of polymer molecule(s) is expressly indicated every reference to “a polymer”, “a polymer molecule”, “the polymer” or “the polymer molecule” contained in a polypeptide of the invention or otherwise used in the present invention shall be a reference to one or more polymer molecule(s).

The term “attachment group” is intended to indicate an amino acid residue group of the polypeptide capable of coupling to the relevant non-polypeptide moiety. For instance, for polymer conjugation, in particular to PEG, a frequently used attachment group is the ε-amino group of lysine or the N-terminal amino group. Other polymer attachment groups include a free carboxylic acid group (e.g., that of the C-terminal amino acid residue or of an aspartic acid or glutamic acid residue), suitably activated carbonyl groups, oxidized carbohydrate moieties and mercapto groups. Useful attachment groups and their matching non-peptide moieties are exemplified in Table 2.

TABLE 2


Attachment		Example of non-peptide	Conjungation method/
Group	Amino Acid	moiety	activated PEG	Reference

—NH₂	N-terminal Lys,	Polymer, e.g., PEG with	mPEG-SPA	Shearwater Corp.
	Arg, His	amide or imine group	Tresylated mPEG	Delgado et al., 1992.
—COOH	C-terminal Asp	Polymer, e.g., PEG with	mPEG-Hz	Shearwater Corp.
	and Glu	ester or amide group	in vitro coupling
		Oligosaccharide moiety
—SH	Cys	Polymer, e.g. PEG, with	PEG vinylsullphone	Shearwater Corp.
		disulfide, maleimide or	PEG-maleimide	Delgado et al., 1992
		vinyl sulfone group	In vitro coupling
		Oligosaccharide moiety
—OH	Ser, Thr, —OH, lys	Oligosaccharide moiety	In vivo O-linked
		PAG with ester, ether,	glycosylation
		carbamate, carbonate
—CONH₂	Asn as part of an	Oligosaccharide moiety	In vivo N-glycosylation
	N-glycosylation	Polymer, e.g. PEG
	site
Aromatic	Phe, Tyr, Trp,	Oligosaxxharide moiety	In vitro coupling	Yan and Wold, 1984
—CONH₂	Gln
Aldehyde	Oxidized	Polymer, e.g. PEG	PEGylation	Andresz et al., 1978
Ketone	oligosaccharide	PEG hydroxide		WO 92/16655
				WO 00/23114
Guanidino	Arg	Oligosaccharide moiety	In vitro coupling	Lunblad and Noyes,
				Chemical reagents for
				protein modification, CRC
				Press
Imidazole	His	Oligosaccharide moiety	In vitro coupling	Lunblad and Noyes,
ring				Chemical reagents for
				protein modification, CRC
				Press

C. Site-Specific Mutagenesis
In one embodiment, amino acid sequence variants of a polypeptide can be prepared. These may, for instance, be minor sequence variants of polypeptides that arise due to natural variation within the population or they may be homologs found in other species. They also may be sequences that do not occur naturally but that are sufficiently similar that they function similarly and/or elicit an immune response that cross-reacts with natural forms of the polypeptide. Sequence variants can be prepared by standard methods of site-directed mutagenesis such as those described below.
Amino acid sequence variants of the polypeptide can be substitutional, insertional, or deletion variants. Deletion variants lack one or more residues of the native protein which are not essential for function or immunogenic activity, and are exemplified by the variants of a receptor lacking a transmembrane sequence.
Substitutional variants typically contain the exchange of one amino acid for another at one or more sites within the protein, and may be designed to modulate one or more properties of the polypeptide such as stability against proteolytic cleavage or immunogenicity. Substitutions preferably are conservative, that is, one amino acid is replaced with one of similar shape and charge. Conservative substitutions are well known in the art and include, for example, the changes of: alanine to serine; arginine to lysine; asparagine to glutamine or histidine; aspartate to glutamate; cysteine to serine; glutamine to asparagine; glutamate to aspartate; glycine to proline; histidine to asparagine or glutamine; isoleucine to leucine or valine; leucine to valine or isoleucine; lysine to arginine; methionine to leucine or isoleucine; phenylalanine to tyrosine, leucine or methionine; serine to threonine; threonine to serine; tryptophan to tyrosine; tyrosine to tryptophan or phenylalanine; and valine to isoleucine or leucine.
Insertional variants include fusion proteins such as those used to allow rapid purification of the polypeptide and also can include hybrid proteins containing sequences from other proteins and polypeptides. For example, an insertional variant could include portions of the amino acid sequence of a polypeptide from one species, together with portions of the homologous polypeptide from another species. Other insertional variants can include those in which additional amino acids are introduced within the coding sequence of the polypeptide, for example a protease cleavage site(s) may be introduced.
Modification and changes may be made in the structure of a polynucleotide and still obtain a functional molecule that encodes a protein or polypeptide with desirable characteristics. The following is a discussion based upon changing the amino acids of a protein to create an equivalent, or even an improved, second-generation molecule. The amino acid changes may be achieved by changing the codons of the DNA sequence, according to the following data.
For example, certain amino acids may be substituted for other amino acids in a protein structure without appreciable loss of interactive binding capacity with structures such as, for example, antigen-binding regions of antibodies or binding sites on substrate molecules. Since it is the interactive capacity and nature of a protein that defines that protein's biological activity certain amino acid substitutions can be made in a protein sequence still obtain a protein with like properties. It is thus contemplated by the inventors that various changes may be made in the DNA sequences of genes, mRNA or polynucleotides without appreciable loss of their biological utility or activity.

In making such changes, the hydropathic index of amino acids may be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a protein is generally understood in the art (Kyte & Doolittle, 1982).

TABLE 3


Amino Acids	Codons

Alanine	Ala	A	GCA GCC GCG GCU

Cysteine	Cys	C	UGC UGU

Aspartic acid	Asp	D	GAC GAU

Glutamic acid	Glu	E	GAA GAG

Phenylalanine	Phe	F	UUC UUU

Glycine	Gly	G	GGA GGC GGG GGU

Histidine	His	H	CAC CAU

Isoleucine	Ile	I	AUA AUC AUU

Lysine	Lys	K	AAA AAG

Leucine	Leu	L	UUA UUG CUA CUC CUG CUU

Methionine	Met	M	AUG

Asparagine	Asn	N	AAC AAU

Proline	Pro	P	CCA CCC CCG CCU

Glutamine	Gln	Q	CAA CAG

Arginine	Arg	R	AGA AGG CGA CGC CGG CGU

Serine	Ser	S	AGC AGU UCA UCC UCG UCU

Threonine	Thr	T	ACA ACC ACG ACU

Valine	Val	V	GUA GUG GUG GUU

Tryptophan	Trp	W	UGG

Tyrosine	Tyr	Y	UAC UAU

It is accepted that the relative hydropathic character of the amino acid contributes to the secondary structure of the resultant protein, which in turn defines the interaction of the protein with other molecules, for example, enzymes, substrates, receptors, DNA, antibodies, antigens, and the like. It is known in the art that certain amino acids may be substituted by other amino acids having a similar hydropathic index or score and still result in a protein with similar biological activity. In making such changes, the substitution of amino acids whose hydropathic indices are within ±2 is preferred, those which are within ±1 are particularly preferred, and those within ±0.5 are even more particularly preferred.
It is also understood in the art that the substitution of like amino acids can be made effectively on the basis of hydrophilicity. U.S. Pat. No. 4,554,101, incorporated herein by reference, states that the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with a biological property of the protein.
It is understood that an amino acid can be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent and immunologically equivalent protein. In such changes, the substitution of amino acids whose hydrophilicity values are within ±2 is preferred, those that are within ±1 are particularly preferred, and those within ±0.5 are even more particularly preferred.
Site-specific mutagenesis is a technique useful in the preparation of individual peptides, or biologically functional equivalent proteins or peptides, through specific mutagenesis of the underlying DNA. The technique further provides a ready ability to prepare and test sequence variants, incorporating one or more of the foregoing considerations, by introducing one or more nucleotide sequence changes into the DNA. In general, the technique of site-specific mutagenesis is well known in the art. The technique typically employs a bacteriophage vector that exists in both a single stranded and double stranded form. Typical vectors useful in site-directed mutagenesis include vectors such as the M13 phage. These phage vectors are commercially available and their use is generally well known to those skilled in the art. Double stranded plasmids are also routinely employed in site-directed mutagenesis, which eliminates the step of transferring the gene of interest from a phage to a plasmid.
The preparation of sequence variants of a GPCR, including but not limted to sCRFR2α, polynucleotide using site-directed mutagenesis is provided as a means of producing potentially useful species, i.e., species with altered ligand binding properties that include an increased affinity for a particular ligand, and is not meant to be limiting, as there are other ways in which sequence variants of nucleic acids may be obtained. For example, recombinant vectors encoding the desired gene may be treated with mutagenic agents, such as hydroxylamine, to obtain sequence variants.
D. Expression and Purification of Polypeptides
The polynucleotides of the invention, in particular 100, 150, 200 250, 300, 400, 450, 500, 550 or more contiguous nucleotides of the DNA encoding a GPCR, a family B GPCR, a family B1 GPCR, or a polynucleotide that is 70, 75, 80, 85, 90, 95, 98, or 100% identical to the sequence specified in the accompaning sequence listing, e.g., SEQ ID NO:1, 3, 5, 7, 9, 11, 13, or 14 can be expressed as encoded peptides or proteins. In a particular aspect the DNA encodes all or part of a GPCR extracellular domain and in particular an amino terminal extracellular domain. The engineering of DNA segment(s) for expression in a prokaryotic or eukaryotic system may be performed by techniques generally known to those of skill in recombinant expression. It is believed that virtually any expression system may be employed in the expression of the claimed nucleic acid sequences.
In certain embodiments, the present invention concerns novel compositions comprising at least one proteinaceous molecule, such as sGPCR, asCRFR, or a sCRFR2. As used herein, a “proteinaceous molecule,” “proteinaceous composition,” “proteinaceous compound,” “proteinaceous chain” or “proteinaceous material” generally refers, but is not limited to, a protein of greater than about 200 amino acids or the full length endogenous sequence translated from a gene; a polypeptide of greater than about 100 amino acids; and/or a peptide of from about 3 to about 100 amino acids. All the “proteinaceous” terms described above may be used interchangeably herein. Furthermore, these terms may be applied to fusion proteins as well.
In certain embodiments the size of the at least one proteinaceous molecule may comprise, but is not limited to, about or at least 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 275, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1750, 2000, 2250, 2500 or greater amino molecule residues, and any range derivable therein, particularly 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or more contiguous amino acid sequences of such lengths of a GPCR, a family B GPCR, a family B1 GPCR, or SEQ ID NO:2, 4, 6, 8, 10, 12 or 15, including the full length of SEQ ID NO:4, 8, 12, or 15. Both cDNA and genomic sequences are suitable for eukaryotic expression, as the host cell will generally process the genomic transcripts to yield functional mRNA for translation into protein.
As used herein, the terms “engineered” and “recombinant” cells are intended to refer to a cell into which an exogenous DNA segment or polynucleotide, such as a cDNA or polynucleotide has been introduced. Therefore, engineered cells are distinguishable from naturally occurring cells which do not contain a recombinantly introduced exogenous DNA segment or gene. Engineered cells are thus cells having a gene or genes introduced through the hand of man. Recombinant cells include those having an introduced cDNA or genomic DNA, and may also include genes positioned adjacent to a promoter not naturally associated with the particular introduced gene.
To express a recombinant protein or polypeptide, whether mutant or wild-type, in accordance with the present invention one would prepare an expression vector that comprises one of the claimed isolated nucleic acids under the control of one or more promoters. To bring a coding sequence “under the control of” a promoter, one positions the 5′ end of the translational initiation site of the reading frame generally between about 1 and 50 nucleotides “downstream” of (i.e., 3′ of) the chosen promoter. The “upstream” promoter stimulates transcription of the inserted DNA and promotes expression of the encoded recombinant protein. This is the meaning of “recombinant expression” in the context used here.
Many standard techniques are available to construct expression vectors containing the appropriate nucleic acids and transcriptional/translational control sequences in order to achieve protein or peptide expression in a variety of host-expression systems. Cell types available for expression include, but are not limited to, bacteria, such as E. coli, B. subtilis, E. coli strain RR1, E. coli LE392, E. coli B, E. coli χ 1776 (ATCC No. 31537) as well as E. coli W3110 (F-, lambda-, prototrophic, ATCC No. 273325); bacilli such as Bacillus subtilis; and other enterobacteriaceae such as Salmonella typhimurium, Serratia marcescens, and various Pseudomonas species transformed with recombinant phage DNA, plasmid DNA or cosmid DNA expression vectors.
The polynucleotide or polynucleotide fragment encoding a polypeptide can be inserted into an expression vector by standard subcloning techniques. In one embodiment, an E. coli expression vector is used that produces the recombinant polypeptide as a fusion protein, allowing rapid affinity purification of the protein. Examples of such fusion protein expression systems are the glutathione S-transferase system (Pharmacia, Piscataway, N.J.), the maltose binding-protein system (New England Biolabs, Beverley, Mass.), the FLAG system (IBI, New Haven, Conn.), and the 6xHis system (Qiagen, Chatsworth, Calif.). Further useful vectors include pIN vectors (Inouye et al., 1985); and pGEX vectors, for use in generating glutathione S-transferase (GST) soluble fusion proteins. Other suitable fusion proteins are those with β-galactosidase, ubiquitin, or the like.
For expression in Saccharomyces, the plasmid YRp7, for example, is commonly used (Stinchcomb et al., 1979; Kingsman et al., 1979; Tschemper et al., 1980). This plasmid contains the trp1 gene, which provides a selection marker for a mutant strain of yeast lacking the ability to grow in tryptophan, for example ATCC No. 44076 or PEP4-1 (Jones, 1977). The presence of the trp1 lesion as a characteristic of the yeast host cell genome then provides an effective environment for detecting transformation by growth in the absence of tryptophan.
Suitable promoting sequences in yeast vectors include the promoters for 3-phosphoglycerate kinase (Hitzeman et al., 1980) or other glycolytic enzymes (Hess et al., 1968; Holland et al., 1978), such as enolase, glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase, and glucokinase. In constructing suitable expression plasmids, the termination sequences associated with these genes are also ligated into the expression vector 3′ of the sequence desired to be expressed to provide polyadenylation of the mRNA and termination.
Other suitable promoters, which have the additional advantage of transcription controlled by growth conditions, include the promoter region for alcohol dehydrogenase 2, isocytochrome C, acid phosphatase, degradative enzymes associated with nitrogen metabolism, and the aforementioned glyceraldehyde-3-phosphate dehydrogenase, and enzymes responsible for maltose and galactose utilization.
In addition to micro-organisms, cultures of cells derived from multicellular organisms may also be used as hosts. In principle, any such cell culture is workable, whether from vertebrate or invertebrate culture including mammalian and insect cells (e.g., U.S. Pat. No. 4,215,051).
Examples of useful mammalian host cell lines are VERO and HeLa cells, Chinese hamster ovary (CHO) cell lines, WI38, BHK, COS-7, 293, HepG2, NIH3T3, RIN and MDCK cell lines. In addition, a host cell may be chosen that modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products may be important for the function of the encoded protein.
Specific initiation signals may also be required for efficient translation of the claimed isolated nucleic acid coding sequences. These signals include the ATG initiation codon and adjacent sequences. Exogenous translational control signals, including the ATG initiation codon, may additionally need to be provided. One of ordinary skill in the art would readily be capable of determining this need and providing the necessary signals. It is well known that the initiation codon must be in-frame (or in-phase) with the reading frame of the desired coding sequence to ensure translation of the entire insert. The efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements or transcription terminators (Bittner et al., 1987).
For long-term, high-yield production of recombinant proteins, stable expression is preferred. For example, cell lines that stably express constructs encoding G-proteins may be engineered. Rather than using expression vectors that contain viral origins of replication, host cells can be transformed with vectors controlled by appropriate expression control elements (e.g., promoter, enhancer, sequences, transcription terminators, polyadenylation sites, etc.), and a selectable marker. Following the introduction of foreign DNA, engineered cells may be allowed to grow for 1-2 days in an enriched medium, and then are switched to a selective medium. The selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci, which in turn can be cloned and expanded into cell lines.
A number of selection systems may be used, including, but not limited, to the herpes simplex virus thymidine kinase (Wigler et al., 1977), hypoxanthine-guanine phosphoribosyltransferase (Szybalska et al., 1962) and adenine phosphoribosyltransferase genes (Lowy et al., 1980), in tk⁻, hgprt⁻ or aprt⁻ cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for dhfr, which confers resistance to methotrexate (Wigler et al., 1980; O'Hare et al., 1981); gpt, which confers resistance to mycophenolic acid (Mulligan et al., 1981); neo, which confers resistance to the aminoglycoside G-418 (Colbere-Garapin et al., 1981); and hygro, which confers resistance to hygromycin.
Once the polynucleotide sequence coding a particular polypeptide has been determined or engineered, the polynucleotide can be inserted into an appropriate expression system. In this case, the inventors contemplate a polynucleotide encoding a sGPCR ligand binding domain polypeptide. The polynucleotide can be expressed in any number of different recombinant DNA expression systems to generate large amounts of the polypeptide product, which can then be purified and/or isolated to be used as a therapeutic or to vaccinate animals to generate antisera, or in certain aspects of the invention as an antagonist of GPCR ligand and/or GPCR activation. In further aspects, sGPCRs of the invention can be used in methods to detect, screen, or identify ligands, receptors, or agonist and/or antagonist of GPCRs. A polynucleotide of the invention may be expressed to obtain a GPCR ligand binding domain, a family B GPCR ligand binding domain, a family B1 GPCR ligand binding domain, a sCRFR ligand binding domain or a CRFR2 ligand binding domain polypeptide comprising an amino acid sequence including all or part of the amino acid sequence as set forth in the sequence listing, e.g., SEQ ID NO:2, 4, 6, 8, 10, 12, or 15.
As an alternative to recombinant polypeptides, synthetic peptides corresponding to the polypeptides of the invention can be prepared, including antigenic peptides. Such antigenic peptides are at least six amino acid residues long, and may contain up to approximately 35 residues. Automated peptide synthesis machines include those available from Applied Biosystems (Foster City, Calif.). Use of such small peptides for vaccination typically requires conjugation of the peptide to an immunogenic carrier protein such as hepatitis B surface antigen, keyhole limpet hemocyanin or bovine serum albumin. Methods for performing this conjugation are well known in the art.
1. Purification of Expressed Proteins
Further aspects of the present invention concern the purification for isolation, and in particular embodiments, the substantial purification, of a protein or peptide comprising all or part of a sGPCR ligand binding domain. The term “purified or isolated protein or peptide” as used herein, is intended to refer to a composition, isolatable from other components, wherein the protein, polypeptide or peptide is purified to any degree relative to its naturally-obtainable state, i.e., in this case, relative to its purity within a organism or tissue. A purified or isolated protein or peptide therefore also refers to a protein or peptide, free from the environment in which it may naturally occur. A purified or isolated protein or polypeptide may have a purity greater than or at least 70, 75, 80, 85, 90, 95, 98, or 99% purity.
Generally, “purified” will refer to a protein or peptide composition that has been subjected to fractionation to remove various other components, and which composition substantially retains its expressed activity. Where the term “substantially purified” is used, this designation will refer to a composition in which the protein or peptide forms the major component of the composition, such as constituting about 50% or more of the proteins in the composition.
Various methods for quantifying the degree of purification of the protein or peptide will be known to those of skill in the art in light of the present disclosure. These include, for example, determining the specific activity (e.g., binding affinity for GPCR ligand including, but not limited to CRF or a ligand of the CRF family) of an active fraction, or assessing the number of polypeptides within a fraction by SDS/PAGE analysis. A preferred method for assessing the purity of a fraction is to calculate the specific activity of the fraction, to compare it to the specific activity of the initial extract, and to thus calculate the degree of purity, herein assessed by a “-fold purification number.” The actual units used to represent the amount of activity, which may include binding activity or affinity, will, of course, be dependent upon the particular assay technique chosen.
Various techniques suitable for use in protein purification will be well known to those of skill in the art. These include, for example, precipitation with ammonium sulphate, polyethylene glycol, antibodies and the like or by heat denaturation, followed by centrifugation; chromatography steps such as ion exchange, gel filtration, reverse phase, hydroxylapatite, and/or affinity chromatography; isoelectric focusing; gel electrophoresis; and combinations of such and other techniques. As is generally known in the art, it is believed that the order of conducting the various purification steps may be changed, or that certain steps may be omitted, and still result in a suitable method for the preparation of a substantially purified protein or peptide.
There is no general requirement that the protein or peptide always be provided in their most purified state. Indeed, it is contemplated that less substantially purified products will have utility in certain embodiments. Partial purification may be accomplished by using fewer purification steps in combination, or by utilizing different forms of the same general purification scheme. For example, it is appreciated that a cation-exchange column chromatography performed utilizing an HPLC apparatus will generally result in a greater-fold purification than the same technique utilizing a low pressure chromatography system. Methods exhibiting a lower degree of relative purification may have advantages in total recovery of protein product, or in maintaining the activity of an expressed protein.
E. Preparation of Antibodies Specific for sGPCRs
For some embodiments, it will be desired to produce antibodies that bind with high specificity to the protein product(s) of an isolated nucleic acid encoding for sGPCR, including but not limted to sCRFR2α. In certain aspects, an antibody preparation is contemplated that recognizes or binds the c-terminus of a GPCR, particularly a splice variant such as a sCRFR2α splice variant and thus can be used to distingush a sGPCR polypeptide from a membrane associated receptor. Such antibodies may be used in any of a variety of applications known to those of skill in the art, including but not limited to: immunodetection methods, immunoprecipitation methods, ELISA assays, protein purification methods, etc. Means for preparing and characterizing antibodies are well known in the art (See, e.g., Harlow and Lane, 1988, incorporated herein by reference).
Methods for generating polyclonal antibodies are well known in the art. Briefly, a polyclonal antibody is prepared by immunizing an animal with an antigenic composition and collecting antisera from that immunized animal. A wide range of animal species can be used for the production of antisera. Typically the animal used for production of antisera is a rabbit, a mouse, a rat, a hamster, a guinea pig, a horse, or a goat. Because of the relatively large blood volume of rabbits, a rabbit is a preferred choice for production of polyclonal antibodies.
As is well known in the art, a given composition may vary in its immunogenicity. It is often necessary therefore to boost the host immune system, as may be achieved by coupling a peptide or polypeptide immunogen to a carrier. Exemplary and preferred carriers are keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA). Other albumins such as ovalbumin, mouse serum albumin or rabbit serum albumin can also be used as carriers. Means for conjugating a polypeptide to a carrier protein are well known in the art and include glutaraldehyde, m-maleimidobenzoyl-N-hydroxysuccinimide ester, carbodiimide and bis-biazotized benzidine.
As is also well known in the art, the immunogenicity of a particular immunogen composition can be enhanced by the use of non-specific stimulators of the immune response, known as adjuvants. Exemplary and preferred adjuvants include complete Freund's adjuvant (a non-specific stimulator of the immune response containing killed Mycobacterium tuberculosis), incomplete Freund's adjuvants and aluminum hydroxide adjuvant.
Monoclonal antibodies (MAbs) may be readily prepared through use of well-known techniques, such as those exemplified in U.S. Pat. No. 4,196,265, incorporated herein by reference. Typically, this technique involves immunizing a suitable animal with a selected immunogen composition, e.g., a purified or partially purified expressed protein, polypeptide or peptide. The immunizing composition is administered in a manner that effectively stimulates antibody producing cells.
The animals are injected with antigen as described above. Following immunization, somatic cells with the potential for producing antibodies, specifically B lymphocytes (B cells), are selected for use in the MAb generating protocol. Often, a panel of animals will have been immunized and the spleen of the animal with the highest antibody titer will be removed and the spleen lymphocytes obtained by homogenizing the spleen with a syringe.
The antibody-producing B lymphocytes from the immunized animal are then fused with cells of an immortal myeloma cell, generally one of the same species as the animal that was immunized. Myeloma cell lines suited for use in hybridoma-producing fusion procedures preferably are non-antibody-producing, have high fusion efficiency, and have enzyme deficiencies that render them incapable of growing in certain selective media that support the growth of only the desired fused cells (hybridomas). Any one of a number of myeloma cells may be used, as are known to those of skill in the art (Goding, 1986). For example, where the immunized animal is a mouse, one may use P3-X63/Ag8, X63-Ag8.653, NS1/1.Ag 4 1, Sp210-Ag14, FO, NSO/U, MPC-11, MPC11-X45-GTG 1.7 and S194/5XX0 Bul; for rats, one may use R210.RCY3, Y3-Ag 1.2.3, IR983F and 4B210; and U-266, GM 1500-GRG2, LICR-LON-HMy2 and UC729-6 are all useful in connection with human cell fusions.
One preferred murine myeloma cell is the NS-1 myeloma cell line (also termed P3-NS-1-Ag4-1), which is readily available from the NIGMS Human Genetic Mutant Cell Repository by requesting cell line repository number GM3573. Another mouse myeloma cell line that may be used is the 8-azaguanine-resistant mouse murine myeloma SP2/0 non-producer cell line.
Large amounts of the monoclonal antibodies of the present invention may also be obtained by multiplying hybridoma cells in vivo. Cell clones are injected into mammals that are histocompatible with the parent cells, e.g., syngeneic mice, to cause growth of antibody-producing tumors. Optionally, the animals are primed with a hydrocarbon, especially oils such as pristane (tetramethylpentadecane) prior to injection.
In accordance with the present invention, fragments of a monoclonal antibody can be obtained by methods which include digestion with enzymes such as pepsin or papain and/or cleavage of disulfide bonds by chemical reduction. Alternatively, monoclonal antibody fragments encompassed by the present invention can be synthesized using an automated peptide synthesizer, or by expression of full-length polynucleotide or of polynucleotide fragments encoding all or part of Mab.
Antibody conjugates may be prepared by methods known in the art, e.g., by reacting an antibody with an enzyme in the presence of a coupling agent such as glutaraldehyde or periodate. Conjugates with fluorescein markers are prepared in the presence of these coupling agents or by reaction with an isothiocyanate. Conjugates with metal chelates are similarly produced. Other moieties to which antibodies may be conjugated include radionuclides such as ³H, ¹²⁵I, ¹³¹I ³²P, ³⁵S, ¹⁴C, ⁵¹Cr, ³⁶Cl, ⁵⁷Co, ⁵⁸Co, ⁵⁹Fe, ⁷⁵Se, ¹⁵²Eu, and ^99mTc. Radioactively labeled antibodies of the present invention can be produced according to well-known methods. For instance, antibodies can be iodinated by contact with sodium or potassium iodide and a chemical oxidizing agent such as sodium hypochlorite, or an enzymatic oxidizing agent, such as lactoperoxidase. Antibodies according to the invention may be labeled with technetium-⁹⁹by ligand exchange process, for example, by reducing pertechnate with stannous solution, chelating the reduced technetium onto a Sephadex column and applying the antibody to this column or by direct labelling techniques, e.g., by incubating pertechnate, a reducing agent such as SnCl₂, a buffer solution such as sodium-potassium phthalate solution, and the antibody.
III. Nucleic Acids Encoding sGPCR Polypeptides
The present invention includes nucleic acids that encode all or part of a sGPCR, such as but not limited to a GPCR, a family B GPCR, a family B1 GPCR, a CRFR, or a CRFR2 polypeptide, and may include various nucleic acid sequences needed for delivery of the nucleic acid sequence as well as the transcription and/or translation of the nucleic acid seqeunce. Nucleic acid molecules of the invention may include various contiguous stretches of the nucleic acid, for example about 10, 15, 17, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 250, 300, 350, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 1750, 2000, 2100, including all or part of the full length nucleic acid sequences in the sequence listing, e.g., SEQ ID NO:1, 3, 5, 7, 9, 11, 13, or 14, or polynucleotides of those GPCRs referenced herein, fragments thereof, mRNAs, or cDNAs comprising sequences described or referenced herein, and mutants of each are contemplated. Also contemplated are molecules that are complementary to the above mentioned sequences and that bind to these sequences under high stringency conditions. These probes will be useful in a variety of hybridization embodiments, such as Southern and northern blotting.
Various probes and primers can be designed around the disclosed nucleotide sequences. Primers may be of any length but, typically, are 10-20 bases in length. In particular aspects, the probe or primer can be used to identify or screen for the presence of an alternatively spliced form of a GPCR, such as but not limited to the CRFR2 gene that includes an exon 5/exon 7 splice junction (may also be described as an exon 3/exon 5 juction as it relates to CRFR2α transcrition). These probes or primers may either hybridize unique sequence of the engineered nulceic acid or splice junction, or amplify a nucleic acid characteristic of the engineered nucleic acid or the splice junction. By assigning numeric values to a sequence, for example, the first residue is 1, the second residue is 2, etc., an algorithm defining all primers can be proposed:
n to n+y
where n is an integer from 1 to the last number of the sequence and y is the length of the primer minus one, where n+y does not exceed the last number of the sequence. Thus, for a 10-mer, the probes correspond to bases 1 to 10, 2 to 11, 3 to 12 . . . and so on. For a 15-mer, the probes correspond to bases 1 to 15, 2 to 16, 3 to 17 . . . and so on. For a 20-mer, the probes correspond to bases 1 to 20, 2 to 21, 3 to 22 . . . and so on.
In certain aspects the nucleic acid seqeunces of the invention may be used to encode various polypeptides described herein. In one embodiment of the present invention, the nucleic acid sequences may be used as hybridization probes or amplification primers. In certain embodiments, these probes and primers consist of oligonucleotide fragments. Such fragments should be of sufficient length to provide specific hybridization to an RNA or DNA sample extracted from tissue. The sequences typically will be 10-20 nucleotides, but may be longer. Longer sequences, e.g., 40, 50, 100, 500 and even up to full length, are preferred for certain embodiments.
The use of a hybridization probe of between 17 and 100 nucleotides in length allows the formation of a duplex molecule that is both stable and selective. Molecules having complementary sequences over stretches greater than 20 bases in length are generally preferred, in order to increase stability and selectivity of the hybrid, and thereby improve the quality and degree of particular hybrid molecules obtained. One will generally prefer to design nucleic acid molecules having stretches of 20 to 30 nucleotides, or even longer where desired. Such fragments may be readily prepared by, for example, directly synthesizing the fragment by chemical means or by introducing selected sequences into recombinant vectors for recombinant production. Accordingly, the nucleotide sequences of the invention may be used for their ability to selectively form duplex molecules with complementary stretches of genes, polynucleotides or RNAs, or to provide primers for amplification of DNA or RNA from tissues. Depending on the application envisioned, one will desire to employ varying conditions of hybridization to achieve varying degrees of selectivity of probe towards target sequence.
For applications requiring high selectivity, one will typically desire to employ relatively stringent or high stringency conditions to form the hybrids, e.g., one will select relatively low salt and/or high temperature conditions, such as provided by about 0.02 M to about 0.10 M NaCl at temperatures of about 50° C. to about 70° C. Such high stringency conditions tolerate little, if any, mismatch between the probe and the template or target strand, and would be particularly suitable for isolating specific genes or detecting specific mRNA transcripts. It is generally appreciated that conditions can be rendered more stringent by the addition of increasing amounts of formamide.
In certain embodiments, it will be advantageous to employ nucleic acid sequences of the present invention in combination with an appropriate means of detection, such as a fluorescent or radiolabel, for determining hybridization. A wide variety of appropriate indicator means are known in the art, including fluorescent, radioactive, enzymatic or other ligands, such as avidin/biotin, which are capable of being detected.
For applications in which the nucleic acid segments of the present invention are incorporated into expression vectors, such as plasmids, cosmids or viral polynucleotides, these segments may be combined with other DNA sequences, such as promoters, polyadenylation signals, restriction enzyme sites, multiple cloning sites, other coding segments, and the like, such that their overall length may vary considerably. It is contemplated that a nucleic acid fragment of almost any length may be employed, with the total length preferably being limited by the ease of preparation and use in the intended recombinant DNA protocol.
DNA segments encoding a specific polynucleotide may be introduced into recombinant host cells and employed for expressing a sGPCR, such as but not limited to a sCRFR2α polypeptide. Alternatively, through the application of genetic engineering techniques, subportions or derivatives of selected polynucleotides may be employed.
Throughout this application, the term “expression construct” is meant to include any type of genetic construct containing a nucleic acid having a sequence defining a product, such as but not limited to a product encoding a polypeptide, in which part or all of the nucleic acid sequence is capable of being transcribed. The transcript may be translated into a protein, but it need not be. Thus, in certain embodiments, expression includes both transcription of a polynucleotide and translation of a RNA into a polypeptide product.
In preferred embodiments, the nucleic acid is under transcriptional control of a promoter. A “promoter” refers to a DNA sequence recognized by the synthetic machinery of the cell, or introduced synthetic machinery, required to initiate the specific transcription of a polynucleotide. The phrase “under transcriptional control” means that the promoter is in the correct location and orientation in relation to the nucleic acid to control RNA polymerase initiation and expression of the polynucleotide. The term promoter will be used here to refer to a group of transcriptional control modules that are clustered around the initiation site for a RNA polymerase, in particular RNA polymerase II. In certain aspects, at least one module in each promoter functions to position the start site for RNA synthesis. The best known example of this is the TATA box, but in some promoters lacking a TATA box, such as the promoter for the mammalian terminal deoxynucleotidyl transferase gene and the promoter for the SV40 late genes, a discrete element overlying the start site itself helps to fix the place of initiation.
The particular promoter that is employed to control the expression of a nucleic acid is not believed to be critical, so long as it is capable of expressing the nucleic acid in the targeted cell. Thus, where a human cell is targeted, it is preferable to position the nucleic acid coding region adjacent to and under the control of a promoter that is capable of being expressed in a human cell. Generally speaking, such a promoter might include either a human or viral promoter.
In various other embodiments, the human cytomegalovirus (CMV) immediate early gene promoter, the SV40 early promoter and the Rous sarcoma virus long terminal repeat can be used to obtain high-level expression of transgenes. The use of other viral or mammalian cellular or bacterial phage promoters which are well-known in the art to achieve expression of a transgene is contemplated as well, provided that the levels of expression are sufficient for a given purpose. Several elements/promoters, as described below, may be employed, in the context of the present invention, to regulate the expression of a polynucleotide, such as a transgene. This list is not intended to be exhaustive of all the possible elements involved in the promotion of transgene expression but, merely, to be exemplary thereof.
Any promoter/enhancer combination (as per the Eukaryotic Promoter Data Base EPDB) could also be used to drive expression of a polynucleotide. Use of a T3, T7 or SP6 cytoplasmic expression system is another possible embodiment. Eukaryotic cells can support cytoplasmic transcription from certain bacterial promoters if the appropriate bacterial polymerase is provided, either as part of the delivery complex or as an additional genetic expression construct. Use of the baculovirus system will involve high level expression from the powerful polyhedrin promoter.
Promoters include, but are not limited to Immunoglobulin Heavy Chain, Immunoglobulin Light Chain, T-Cell Receptor, HLA DQ α and DQ β, β-Interferon, Interleukin-2, Interleukin-2 Receptor, MHC Class II 5, MHC Class II HLA-DRα, β-Actin, Muscle Creatine Kinase, Prealbumin (Transthyretin), Elastase I, Metallothionein, Collagenase, Albumin Gene, α-Fetoprotein, α-Globin, β-Globin, c-fos, c-HA-ras, Insulin, Neural Cell Adhesion Molecule (NCAM), α₁-Anti-trypsin, H2B (TH2B) Histone, Mouse or Type I Collagen, Glucose-Regulated Proteins (GRP94 and GRP78), Rat Growth Hormone, Human Serum Amyloid A (SAA), Troponin I (TN I), Platelet-Derived Growth Factor, Duchenne Muscular Dystrophy, SV40, Polyoma, Retroviruses, Papilloma Virus, Hepatitis B Virus, Human Immunodeficiency Virus, Cytomegalovirus, Gibbon Ape Leukemia Virus.
Various element (inducers) include, but are not limited to MT II (Phorbol Ester (TPA) Heavy metals); MMTV (Glucocorticoids, β-Interferon, poly(rI)X, poly(rc)); Adenovirus 5 E2 (E1a); c-jun (Phorbol Ester (TPA), H₂O₂); Collagenase (Phorbol Ester (TPA)); Stromelysin (Phorbol Ester (TPA), IL-1); SV40 (Phorbol Ester (TPA)); Murine MX Gene (Interferon, Newcastle Disease Virus); GRP78 Gene (A23187); α-2-Macroglobulin (IL-6); Vimentin (Serum); MHC Class I Gene H-2kB (Interferon); HSP70 (E1a, SV40 Large T Antigen); Proliferin (Phorbol Ester-TPA); Tumor Necrosis Factor (FMA); and Thyroid Stimulating Hormone α Gene (Thyroid Hormone).
One will typically include a polyadenylation signal to effect proper polyadenylation of the transcript. The nature of the polyadenylation signal is not believed to be crucial to the successful practice of the invention, and any such sequence may be employed. Preferred embodiments include the SV40 polyadenylation signal and the bovine growth hormone polyadenylation signal, convenient and known to function well in various target cells. Also contemplated is the inclusion of a terminator as an element of an expression cassette. These elements can serve to enhance message levels and to minimize read through from the cassette into other sequences.
In various embodiments of the invention, an expression construct may comprise a virus or engineered construct derived from a viral genome. The ability of certain viruses to enter cells via receptor-mediated endocytosis and to integrate into the host cell genome and express viral genes stably and efficiently have made them attractive candidates for the transfer of foreign genes into mammalian cells (Ridgeway, 1988; Nicolas and Rubenstein, 1988; Baichwal and Sugden, 1986; Temin, 1986). The first viruses used as vectors were DNA viruses including the papovaviruses (simian virus 40, bovine papilloma virus, and polyoma) (Ridgeway, 1988; Baichwal and Sugden, 1986) and adenoviruses (Ridgeway, 1988; Baichwal and Sugden, 1986) and adeno-associated viruses. Retroviruses also are attractive gene transfer vehicles (Nicolas and Rubenstein, 1988; Temin, 1986) as are vaccina virus (Ridgeway, 1988) and adeno-associated virus (Ridgeway, 1988). Such vectors may be used to (i) transform cell lines in vitro for the purpose of expressinG-proteins of interest or (ii) to transform cells in vitro or in vivo to provide therapeutic polypeptides in a gene therapy scenario.
In an alternative embodiment, the sGPCR encoding nucleic acids employed may actually encode antisense constructs that hybridize, under intracellular conditions, to a sGPCR or other encoding nucleic acid. The term “antisense construct” is intended to refer to nucleic acids, preferably oligonucleotides, complementary to the base sequences of a target DNA or RNA.
As used herein, the terms “complementary” means nucleic acid sequences that are substantially complementary over their entire length and have very few base mismatches. For example, nucleic acid sequences of fifteen bases in length may be termed complementary when they have a complementary nucleotide at thirteen or fourteen positions with only a single mismatch. Naturally, nucleic acid sequences which are “completely complementary” will be nucleic acid sequences which are entirely complementary throughout their entire length and have no base mismatches.
A. Detection and Quantitation of Nucleic Acids
One embodiment of the instant invention comprises a method for identification of sGPCR nucleic acid, such as but not limited to CRFR2α nucleic acids, in a biological sample by amplifying and detecting nucleic acids corresponding to sGPCR. The biological sample can be any tissue or fluid in which the polynucleotide might be present. Nucleic acid used as a template for amplification is isolated from cells contained in the biological sample, according to standard methodologies (Sambrook et al., 1989). The nucleic acid may be fractionated or whole cell RNA.
Pairs of primers that selectively hybridize to nucleic acids corresponding to sGPCR are contacted with the isolated nucleic acid under conditions that permit selective hybridization. Once hybridized, the nucleic acid:primer complex is contacted with one or more enzymes that facilitate template-dependent nucleic acid synthesis. Multiple rounds of amplification, also referred to as “cycles,” are conducted until a sufficient amount of amplification product is produced. The amplification products may be detected. In certain applications, the detection may be performed by visual means. Alternatively, the detection may involve indirect identification of the product via chemiluminescence, radioactive scintigraphy of incorporated radiolabel or fluorescent label, or even via a system using electrical or thermal impulse signals (Affymax technology; Bellus, 1994).
A number of template dependent processes are available to amplify the marker sequences present in a given template sample. One of the best known amplification methods is the polymerase chain reaction (referred to as PCR) which is described in detail in U.S. Pat. Nos. 4,683,195, 4,683,202 and 4,800,159, and in Innis et al., 1990, each of which is incorporated herein by reference in its entirety. Polymerase chain reaction methodologies are well known in the art.
Another method for amplification is the ligase chain reaction (“LCR”), disclosed in EPA No. 320 308, which is incorporated herein by reference in its entirety. U.S. Pat. No. 4,883,750 describes a method similar to LCR for binding probe pairs to a target sequence. Also, Qbeta Replicase, described in PCT Application No. PCT/US87/00880, may be used as still another amplification method in the present invention. An isothermal amplification method, in which restriction endonucleases and ligases are used to achieve the amplification of target molecules that contain nucleotide 5′-[alpha-thio]-triphosphates in one strand of a restriction site may also be useful in the amplification of nucleic acids in the present invention, Walker et al., (1992), incorporated herein by reference in its entirety. Still further, Strand Displacement Amplification (SDA) is another method of carrying out isothermal amplification of nucleic acids which involves multiple rounds of strand displacement and synthesis, i.e., nick translation. A similar method, called Repair Chain Reaction (RCR), involves annealing several probes throughout a region targeted for amplification, followed by a repair reaction in which only two of the four bases are present. Target specific sequences can also be detected using a cyclic probe reaction (CPR). Still another amplification method described in GB Application No. 2 202 328, and in PCT Application No. PCT/US89/01025, each of which is incorporated herein by reference in its entirety, may be used in accordance with the present invention. Other nucleic acid amplification procedures include transcription-based amplification systems (TAS), including nucleic acid sequence based amplification (NASBA) and 3SR (Kwoh et al., 1989); PCT Application WO 88/10315, incorporated herein by reference in their entirety).
Following amplification, it may be desirable to separate the amplification product from the template and the excess primer for the purpose of determining whether specific amplification has occurred. In one embodiment, amplification products are separated by agarose, agarose-acrylamide or polyacrylamide gel electrophoresis using standard methods. See Sambrook et al., 1989.
Chromatographic techniques may be employed to effect separation. There are many kinds of chromatography which may be used in the present invention: adsorption, partition, ion-exchange and molecular sieve, and many specialized techniques for using them including column, paper, thin-layer and gas chromatography (Freifelder, 1982).
IV. Methods for sGPCR Gene Expression
In one embodiment of the present invention, there are provided methods for increased sGPCR expression in a cell, such as but not limited to sCRFR2α expression. This is particularly useful where there is an aberration in the protein or protein expression is not sufficient for normal function. This will allow for the alleviation of symptoms of disease experienced as a result of deficiency of sGPCR, hyperactivation of GPCR or an abundance of GPCR ligand.
The general approach to increasing sGPCR is to contact or administer to a cell, tissue, animal, or subject a sGPCR polypeptide. While it is preferred that the protein may be delivered directly, a conceivable embodiment involves providing a nucleic acid encoding a sGPCR polypeptide to the cell or neighboring cells. Following this provision, the sGPCR polypeptide is synthesized by the host cell's transcriptional and translational machinery, as well as any that may be provided by the expression construct. Cis-acting regulatory elements necessary to support the expression of the sGPCR polynucleotide will be provided, in the form of an expression construct. It also is possible that expression of virally-encoded sGPCR could be stimulated or enhanced, or the expressed polypeptide be stabilized, thereby achieving the same or similar effect.
In order to effect expression of constructs encoding sGPCR polynucleotides, the expression construct must be delivered by a delivery vector into a cell. One mechanism for delivery is via viral infection, where the expression construct is encapsidated in a viral particle which will deliver either a replicating or non-replicating nucleic acid.
The ability of certain viruses to enter cells via receptor-mediated endocytosis, to integrate into host cell genome and express viral genes stably and efficiently have made them attractive candidates for the transfer of foreign genes into mammalian cells (Ridgeway, 1988; Nicolas and Rubenstein, 1988; Baichwal and Sugden, 1986; Temin, 1986). The first viruses used as gene vectors were DNA viruses including the papovaviruses (simian virus 40, bovine papilloma virus, and polyoma) (Ridgeway, 1988; Baichwal and Sugden, 1986) and adenoviruses (Ridgeway, 1988; Baichwal and Sugden, 1986). These have a relatively low capacity for foreign DNA sequences and have a restricted host spectrum. Furthermore, their oncogenic potential and cytopathic effects in permissive cells raise safety concerns. They can accommodate only up to 8 kb of foreign genetic material but can be readily introduced in a variety of cell lines and laboratory animals (Nicolas and Rubenstein, 1988; Temin, 1986).
The retroviruses are a group of single-stranded RNA viruses characterized by an ability to convert their RNA to double-stranded DNA in infected cells; they can also be used as vectors. Other viral vectors may be employed as expression constructs in the present invention. Vectors derived from viruses such as vaccinia virus (Ridgeway, 1988; Baichwal and Sugden, 1986; Coupar et al., 1988) adeno-associated virus (AAV) (Ridgeway, 1988; Baichwal and Sugden, 1986; Hermonat and Muzycska, 1984) and herpesviruses may be employed. They offer several attractive features for various mammalian cells (Friedmann, 1989; Ridgeway, 1988; Baichwal and Sugden, 1986; Coupar et al., 1988; Horwich et al., 1990).
Several non-viral methods for the transfer of expression constructs into cultured mammalian cells also are contemplated by the present invention. These include calcium phosphate precipitation (Graham and Van Der Eb, 1973; Chen and Okayama, 1987; Rippe et al., 1990) DEAE-dextran (Gopal, 1985), electroporation (Tur-Kaspa et al., 1986; Potter et al., 1984), direct microinjection (Harland and Weintraub, 1985), DNA-loaded liposomes (Nicolau and Sene, 1982; Fraley et al., 1979) and lipofectamine-DNA complexes, cell sonication (Fechheimer et al., 1987), gene bombardment using high velocity microprojectiles (Yang et. al., 1990), and receptor-mediated transfection (Wu and Wu, 1987; Wu and Wu, 1988). Some of these techniques may be successfully adapted for in vivo or ex vivo use, as discussed below.
In another embodiment of the invention, the expression construct may simply consist of naked recombinant DNA or plasmids. Transfer of the construct may be performed by any of the methods mentioned above which physically or chemically permeabilize the cell membrane. This is particularly applicable for transfer in vitro, but it may be applied to in vivo use as well. Another embodiment of the invention for transferring a naked DNA expression construct into cells may involve particle bombardment. This method depends on the ability to accelerate DNA coated microprojectiles to a high velocity allowing them to pierce cell membranes and enter cells without killing them (Klein et al., 1987). Several devices for accelerating small particles have been developed. One such device relies on a high voltage discharge to generate an electrical current, which in turn provides the motive force (Yang et al., 1990). The microprojectiles used have consisted of biologically inert substances such as tungsten or gold beads.
In a further embodiment of the invention, the expression construct may be entrapped in a liposome. Liposomes are vesicular structures characterized by a phospholipid bilayer membrane and an inner aqueous medium. Multilamellar liposomes have multiple lipid layers separated by aqueous medium. They form spontaneously when phospholipids are suspended in an excess of aqueous solution. The lipid components undergo self-rearrangement before the formation of closed structures and entrap water and dissolved solutes between the lipid bilayers (Ghosh and Bachhawat, 1991). Also contemplated are lipofectamine-DNA complexes.
Other expression constructs which can be employed to deliver a nucleic acid encoding a sCRFR2α polynucleotide into cells are receptor-mediated delivery vehicles. These take advantage of the selective uptake of macromolecules by receptor-mediated endocytosis in almost all eukaryotic cells. Because of the cell type-specific distribution of various receptors, the delivery can be highly specific (Wu and Wu, 1993).
V. Pharmaceuticals and Methods for the Treatment of Disease
In additional embodiments, the present invention concerns formulation of one or more of the polynucleotide, polypeptide, and/or antibody compositions disclosed herein in pharmaceutically-acceptable solutions for administration to a cell, tissue, animal, patient, or subject either alone, or in combination with one or more other modalities of therapy.
Aqueous pharmaceutical compositions of the present invention will have an effective amount of a sGPCR expression construct, an expression construct that encodes a therapeutic gene along with sGPCR, or a sGPCR protein and/or compound that modulates GPCR ligand activity or sensititvy, or other endocrine function. Such compositions generally will be dissolved or dispersed in a pharmaceutically acceptable carrier or aqueous medium. An “effective amount,” for the purposes of therapy, is defined at that amount that causes a clinically measurable difference in the condition of the subject. This amount will vary depending on the substance, the condition of the patient, the type of treatment, etc.
The phrases “pharmaceutically or pharmacologically acceptable” refer to molecular entities and compositions that do not produce a significant adverse, allergic or other untoward reaction when administered to an animal, or human. As used herein, “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredients, its use in the therapeutic compositions is contemplated.
In addition to the compounds formulated for parenteral administration, such as those for intravenous or intramuscular injection, other pharmaceutically acceptable forms include, e.g., tablets or other solids for oral administration; time release capsules; and any other form currently used, including creams, lotions, inhalants and the like.
The active compounds of the present invention will often be formulated for parenteral administration, e.g., formulated for injection via the intravenous, intramuscular, subcutaneous, or even intraperitoneal routes. The preparation of an aqueous composition that contains sGPCR alone or in combination with a conventional therapeutic agent as active ingredients will be known to those of skill in the art in light of the present disclosure. Typically, such compositions can be prepared as injectables, either as liquid solutions or suspensions; solid forms suitable for using to prepare solutions or suspensions upon the addition of a liquid prior to injection can also be prepared; and the preparations can also be emulsified.
The pharmaceutical forms suitable for injectable use include sterile aqueous solutions or dispersions; formulations including sesame oil, peanut oil or aqueous propylene glycol; and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In many cases, the form must be sterile and must be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms, such as bacteria and fungi.
The carrier also can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.
Sterile injectable solutions are prepared by incorporating the active compounds in the required amount in the appropriate solvent with various other ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum-drying and freeze-drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.
Upon formulation, solutions will be administered in a manner compatible with the dosage formulation and in such amount as is therapeutically effective. The formulations are easily administered in a variety of dosage forms, such as the type of injectable solutions described above, with even drug release capsules and the like being employable.
For parenteral administration in an aqueous solution, for example, the solution should be suitably buffered if necessary and the liquid diluent first rendered isotonic with sufficient saline or glucose. These particular aqueous solutions are especially suitable for intravenous, intramuscular, subcutaneous and intraperitoneal administration. In this connection, sterile aqueous media which can be employed will be known to those of skill in the art in light of the present disclosure. For example, one dosage could be dissolved in 1 mL of isotonic NaCl solution and either added to 1000 mL of hypodermoclysis fluid or injected at the proposed site of infusion, (see for example, “Remington's Pharmaceutical Sciences” (1980)). Some variation in dosage will necessarily occur depending on the condition of the subject being treated. The person responsible for administration will, in any event, determine the appropriate dose for the individual subject.
In certain aspects of the methods of the invention, the route the therapeutic composition is administered may be by parenteral administration. The parenteral administration may be intravenous injection, subcutaneous injection, intramuscular injection, intramedullary injection, ingestion or a combination thereof. In certain aspects, the composition comprising sGPCR is administered from about 0.1 to about 10 microgram/kg/body weight per dose. In certain aspects, the composition comprising sGPCR is administered from about 1 to about 5 microgram/kg/body weight per dose. In certain aspects, the composition comprising sGPCR is administered from about 1.2 to about 3.6 microgram/kg/body weight per dose. In certain aspects, the composition comprising sGPCR is administered from about 1.2 to about 2.4 microgram/kg/body weight per dose. In preferred aspects, the amount of sGPCR administered per dose may be about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3.0, abot 3.1, about 3.2, about 3.3, about 3.4, about 3 5, about 3.6, about 3.7, about 3.8, about 3.9, about 4.0, about 4.1, about 4.2, about 4.3, about 4.4, about 4.5, about 4.6, about 4.7, about 4.8, abotu 4.9, about 5.0, about 5.1, about 5.2, about 5.3, about 5.4, about 5.5, about 5.6, about 5.7, about 5.8, about 5.9, about 6.0, about 6.1, about 6.2, about 6.3, about 6.4, about 6.5, about 6.6, about 6.7, about 6.8, about 6.9, about 7.0, about 7.1, about 7.2, about 7.3, about 7.4, about 7.5, about 7.6, about 7.7, about 7.8, about 7.9, about 8.0, about 8.1, about 8.2, about 8.3, about 8.4, about 8.5, about 8.6, about 8.7, about 8.8, about 8.9, about 9.0, about 9.1, about 9.2, about 9.3, about 9.4, about 9.5, about 9.6, about 9.7, about 9.8, about 9.9, about 10.0, or more micrograms/kg/body.
Formulation of pharmaceutically-acceptable excipients and carrier solutions is well-known to those of skill in the art, as is the development of suitable dosing and treatment regimens for using the particular compositions described herein in a variety of treatment regimens, including e.g., oral, parenteral, intravenous, intranasal, and intramuscular administration and formulation.
A. Alimentary Delivery
The term “alimentary delivery” refers to the administration, directly or otherwise, to a portion of the alimentary canal of an animal. The term “alimentary canal” refers to the tubular passage in an animal that functions in the digestion and absorption of food and the elimination of food residue, which runs from the mouth to the anus, and any and all of its portions or segments, e.g., the oral cavity, the esophagus, the stomach, the small and large intestines and the colon, as well as compound portions thereof such as, e.g., the gastro-intestinal tract. Thus, the term “alimentary delivery” encompasses several routes of administration including, but not limited to, oral, rectal, endoscopic and sublingual/buccal administration. A common requirement for these modes of administration is absorption over some portion or all of the alimentary tract and a need for efficient mucosal penetration of the nucleic acid(s) so administered.
1. Oral Delivery
In certain applications, the pharmaceutical compositions disclosed herein may be delivered via oral administration to an animal, patient, or subject. As such, these compositions may be formulated with an inert diluent or with an assimilable edible carrier, or they may be enclosed in hard- or soft-shell gelatin capsule, or they may be compressed into tablets, or they may be incorporated directly with the food of the diet.
The active components may even be incorporated with excipients and used in the form of ingestible tablets, buccal tables, troches, capsules, elixirs, suspensions, syrups, wafers, and the like (Mathiowitz et al., 1997; Hwang et al., 1998; U.S. Pat. Nos. 5,641,515; 5,580,579 and 5,792,451, each specifically incorporated herein by reference in its entirety). The tablets, troches, pills, capsules and the like may also contain the following: a binder, as gum tragacanth, acacia, cornstarch, or gelatin; excipients, such as dicalcium phosphate; a disintegrating agent, such as corn starch, potato starch, alginic acid and the like; a lubricant, such as magnesium stearate; and a sweetening agent, such as sucrose, lactose or saccharin may be added or a flavoring agent, such as peppermint, oil of wintergreen, or cherry flavoring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills, or capsules may be coated with shellac, sugar, or both. A syrup of elixir may contain the active component sucrose as a sweetening agent methyl and propylparabens as preservatives, a dye and flavoring, such as cherry or orange flavor. Of course, any material used in preparing any dosage unit form should be pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, the active compounds may be incorporated into sustained-release preparation and formulations.
Typically, these formulations may contain at least about 0.1% of the active compound or more, although the percentage of the active ingredient(s) may, of course, be varied and may conveniently be between about 1 or 2% and about 60% or 70% or more of the weight or volume of the total formulation. Naturally, the amount of active compound(s) in each therapeutically useful composition may be prepared is such a way that a suitable dosage will be obtained in any given unit dose of the compound. Factors such as solubility, bioavailability, biological half-life, route of administration, product shelf life, as well as other pharmacological considerations will be contemplated by one skilled in the art of preparing such pharmaceutical formulations, and as such, a variety of dosages and treatment regimens may be desirable.
2. Rectal Administration
Therapeutics administered by the oral route can often be alternatively administered by the lower enteral route, i.e., through the anal portal into the rectum or lower intestine. Rectal suppositories, retention enemas or rectal catheters can be used for this purpose and may be preferred when patient compliance might a otherwise be difficult to achieve (e.g., in pediatric and geriatric applications, or when the patient is vomiting or unconscious). Rectal administration may result in more prompt and higher blood levels than the oral route, but the converse may be true as well (Harvey, 1990). Because about 50% of the therapeutic that is absorbed from the rectum will bypass the liver, administration by this route significantly reduces the potential for first-pass metabolism (Benet et al., 1996).
B. Parenteral Delivery
The term “parenteral delivery” refers to the administration of a therapeutic of the invention to an animal, patient or subject in a manner other than through the digestive canal. Means of preparing and administering parenteral pharmaceutical compositions are known in the art (see, e.g., Avis, 1990).
C. Intraluminal Administration
Intraluminal administration, for the direct delivery of a therapeutic to an isolated portion of a tubular organ or tissue (e.g., such as an artery, vein, ureter or urethra), may be desired for the treatment of patients with diseases or conditions afflicting the lumen of such organs or tissues. To effect this mode of administration, a catheter or cannula is surgically introduced by appropriate means. After isolation of a portion of the tubular organ or tissue for which treatment is sought, a composition comprising a therapeutic of the invention is infused through the cannula or catheter into the isolated segment. After incubation for from about 1 to about 120 minutes, during which the therapeutic is taken up or in contact with the cells of the interior lumen of the vessel, the infusion cannula or catheter is removed and flow within the tubular organ or tissue is restored by removal of the ligatures which effected the isolation of a segment thereof (Morishita et al., 1993). Therapeutic compositions of the invention may also be combined with a biocompatible matrix, such as a hydrogel material, and applied directly to vascular tissue in vivo.
D. Intraventricular Administration
Intraventricular administration, for the direct delivery of a therapeutic to the brain of a patient, may be desired for the treatment of patients with diseases or conditions afflicting the brain. One method to affect this mode of administration, a silicon catheter is surgically introduced into a ventricle of the brain of a human patient, and is connected to a subcutaneous infusion pump (Medtronic Inc., Minneapolis, Minn.) that has been surgically implanted in the abdominal region (Zimm et al., 1984; Shaw, 1993). The pump is used to inject the therapeutic and allows precise dosage adjustments and variation in dosage schedules with the aid of an external programming device. The reservoir capacity of the pump is 18-20 mL and infusion rates may range from 0.1 mL/h to 1 mL/h. Depending on the frequency of administration, ranging from daily to monthly, and the dose of drug to be administered, ranging from 0.01 μg to 100 g per kg of body weight, the pump reservoir may be refilled at 3-10 week intervals. Refilling of the pump may be accomplished by percutaneous puncture of the self-sealing septum of the pump.
E. Intrathecal Drug Administration
Intrathecal drug administration, for the introduction of a therapeutic into the spinal column of a patient may be desired for the treatment of patients with diseases of the central nervous system. To effect this route of administration, a silicon catheter may be surgically implanted into the L3-4 lumbar spinal interspace of a human patient, and is connected to a subcutaneous infusion pump which has been surgically implanted in the upper abdominal region (Luer and Hatton, 1993; Ettinger et al., 1978; Yaida et al., 1995). The pump is used to inject the therapeutic and allows precise dosage adjustments and variations in dose schedules with the aid of an external programming device. The reservoir capacity of the pump is 18-20 mL, and infusion rates may vary from 0.1 mL/h to 1 mL/h. Depending on the frequency of drug administration, ranging from daily to monthly, and dosage of drug to be administered, ranging from 0.01 μg to 100 g per kg of body weight, the pump reservoir may be refilled at 3-10 week intervals. Refilling of the pump is accomplished by a single percutaneous puncture to the self-sealing septum of the pump.
To effect delivery to areas other than the brain or spinal column via this method, the silicon catheter is configured to connect the subcutaneous infusion pump to, e.g., the hepatic artery, for delivery to the liver (Kemeny et al., 1993).
F. Vaginal Delivery
Vaginal delivery provides local treatment and avoids first pass metabolism, degradation by digestive enzymes, and potential systemic side-effects. Vaginal suppositories (Block, Chapter 87 In: Remington's Pharmaceutical Sciences, 18th Ed., Gennaro, ed., Mack Publishing Co., Easton, Pa., 1990, pages 1609-1614) or topical ointments can be used to effect this mode of delivery.
G. Liposome-, Nanocapsule-, and Microparticle-Mediated Delivery
In certain embodiments, the inventors contemplate the use of liposomes, nanocapsules, microparticles, microspheres, lipid particles, vesicles, and the like, for the introduction of the compositions of the present invention into suitable host cells. In particular, the compositions of the present invention may be formulated for delivery either encapsulated in a lipid particle, a liposome, a vesicle, a nanosphere, or a nanoparticle or the like.
Such formulations may be preferred for the introduction of pharmaceutically-acceptable formulations of the nucleic acids or constructs disclosed herein. The formation and use of liposomes is generally known to those of skill in the art (see for example, Couvreur et al., 1977; Lasic, 1998; which describes the use of liposomes and nanocapsules in the targeted antibiotic therapy for intracellular bacterial infections and diseases). Recently, liposomes were developed with improved serum stability and circulation half-times (Gabizon and Papahadjopoulos, 1988; Allen and Choun, 1987; U.S. Pat. No. 5,741,516, specifically incorporated herein by reference in its entirety). Further, various methods of liposome and liposome like preparations as potential drug carriers have been reviewed (Takakura, 1998; Chandran et al., 1997; Margalit, 1995; U.S. Pat. Nos. 5,567,434; 5,552,157; 5,565,213; 5,738,868 and 5,795,587, each specifically incorporated herein by reference in its entirety).
Liposomes are formed from phospholipids that are dispersed in an aqueous medium and spontaneously form multilamellar concentric bilayer vesicles (also termed multilamellar vesicles (MLVs). MLVs generally have diameters of from 25 nm to 4 μm. Sonication of MLVs results in the formation of small unilamellar vesicles (SUVs) with diameters in the range of 200 to 500 Å, containing an aqueous solution in the core.
The fate and disposition of intravenously injected liposomes depend on their physical properties, such as size, fluidity, and surface charge. They may persist in tissues for h or days, depending on their composition, and half lives in the blood range from min to several h. Larger liposomes, such as MLVs and LUVs, are taken up rapidly by phagocytic cells of the reticuloendothelial system, but physiology of the circulatory system restrains the exit of such large species at most sites. They can exit only in places where large openings or pores exist in the capillary endothelium, such as the sinusoids of the liver or spleen. Thus, these organs are the predominate site of uptake. On the other hand, SUVs show a broader tissue distribution but still are sequestered highly in the liver and spleen. In general, this in vivo behavior limits the potential targeting of liposomes to only those organs and tissues accessible to their large size. These include the blood, liver, spleen, bone marrow, and lymphoid organs.
Alternatively, the invention provides for pharmaceutically-acceptable nanocapsule formulations of the compositions of the present invention. Nanocapsules can generally entrap compounds in a stable and reproducible way (Henry-Michelland et al., 1987; Quintanar-Guerrero et al., 1998; Douglas et al., 1987). To avoid side effects due to intracellular polymeric overloading, such ultrafine particles (sized around 0.1 μm) should be designed using polymers able to be degraded in vivo. Biodegradable polyalkyl-cyanoacrylate nanoparticles that meet these requirements are contemplated for use in the present invention. Such particles may be are easily made, as described (Couvreur et al., 1980; 1988; zur Muhlen et al., 1998; Zambaux et al. 1998; Pinto-Alphandry et al. , 1995 and U.S. Pat. No. 5,145,684, specifically incorporated herein by reference in its entirety).

EXAMPLES

The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion. One skilled in the art will appreciate readily that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those objects, ends and advantages inherent herein. The present examples, along with the cells and methods described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses which are encompassed within the spirit of the invention as defined by the scope of the claims will occur to those skilled in the art.
A. Materials and Methods
Isolation of the mouse soluble CRFR2α cDNA. The soluble CRFR2α splice variant was isolated in parallel with that of the mouse CRFR2α ortholog. PCR primers were designed based on the homology between known mammalian CRFR2 genes. The following oligonucleotide primers, 5′ CCCCGAAGCTGCCCGACTGG 3′ (SEQ ID NO:16) (sense) and 5′ GGAAGGCTGTAAAGGATGGAGAAG 3′ (SEQ ID NO:17) (antisense) were used to screen cDNA prepared from mouse whole brain poly(A)+ RNA which was reverse transcribed using oligo dT or random primers. PCR was performed at 62° C. for 35 cycles with 90 sec extension at 72° C. The amplified fragments were subcloned into pCRIITOPO vector (Invitrogen, Carlsbad, Calif.), sequenced, and found to encode the full-length CRFR2α novel splice variant lacking exon six, sCRFR2α (Chen et al., 2005).
Semi-quantitative RT-PCR and Southern analysis. The following mouse peripheral and CNS tissues were dissected and directly subjected to total RNA isolation as previously described (Chen et al., 2005): total brain, olfactory bulb, hypothalamus, cortex, cerebellum, hippocampus, midbrain, pons/medulla oblongata, spinal cord and pituitary. The cDNA products were used as templates for semi-quantitative and RT PCR analysis using specific primers for CRFR2α, sCRFR2α and the ribosomal protein S 16. The locations of the oligonuleotide primers at exons three and seven result in the amplification of two products of 418 and 309 corresponding to CRFR2α and sCRFR2α, respectively. Oligonucleotide primers sequence and PCR conditions can be found in the supporting text.
Extracellular receptor kinase 1/2 (ERK1/2) assay. CATH.a cells were equilibrated with DMEM supplemented with 1% (w/v) bovine serum albumin (BSA) for 6 hr and then stimulated with 0.1% DMEM/BSA (vehicle) or 10 nM Ucn I in the presence or absence of 0.4 or 4 nM sCRFR2α diluted in 0.1% DMEM/BSA. Cells were harvested immediately and analyzed for phosphorylated ERK1/2-p42, 44, as previously described (Chen et al., 2005).
Transient transfections and luciferase assay. The HEK293T cells were transfected with a luciferase reporter containing a fragment of the EVX1 gene containing a potent CRE site. The cells were harvested and the luciferase reporter activity was assayed as previously described (Chen et al., 2005). Twenty hours posttransfection, cells were treated for 4 h with vehicle or with Ucn 1 (0.0001-100 nM) in the presence or absence of 0.1 nM sCRFR2α.
Radio-Immuno Assays (RIA). Antisera was raised in rabbits immunized with a synthetic peptide fragment encoding the unique C-terminal tail (aa 113-143) of mouse sCRFR2α conjugated to Keyhole Limpet Hemocyanin using a protocol previously described for inhibin subunits (Vaughan et al., 1989). The analog Tyr¹¹³sCRFR2α (113-143) was radiolabelled with Na¹²⁵I using chloramine-T and purified by HPLC (Vaughan et al., 1989) for use as tracer in the HA. The procedure for sCRFR2α RIA was similar to that previously described in detail for inhibin subunits (Vaughan et al., 2005). Briefly, anti-sCRFR2α was used at 1/300,000 final dilution and synthetic sCRFR2α (113-143) was used as standard. Murine tissues were acid extracted and partially purified using octadecyl silica cartridges as described (Vaughan et al., 1989). Lyophilized samples were tested at three to seven dose levels. Free tracer was separated from bound by the addition of sheep anti-rabbit γ-globulins and 10% (wt/vol) polyethylene glycol. The EC50 and minimum detectable dose for sCRFR2α are ˜5 pg and 100 pg per tube, respectively.
Immunohistochemistry. Adult male C57B6J mice (Jackson Laboratories) and Sprague-Dawley albino rats (Harlan Sprague-Dawley) were anesthetized with chloral hydrate (350 mg/kg, ip) and perfused with Zamboni's fixative (Bittencourt et al., 1999), followed by 0-4 hr. post-fixation. Regularly spaced (1-in-4) series of 30 μm thick frontal sections throughout the brain were prepared for nickel-enhanced avidin-biotin-immunoperoxidase localization of sCRFR2α-ir using Vectastain Elite reagents (Vector Laboratories, Burlingame, Calif.). Primary sCRFR2α antisera were adsorbed against the carrier, affinity purified and used at a dilution of 1:2000. Specificity of immunostaining was evaluated using primary antisera preincubated overnight at 4° C. with 0-300 μM synthetic immunogen. Labeling was also evaluated in mutant mice deficient in either or both CRFRs (Smith et al., 1998; Bale et al. 2000). Detailed description of the fluorescence immunocytochemical analysis of COSM6 cells transfected with sCRFR2α can be found in the supporting text.
Mammalian expression of sCRFR2α: A cDNA corresponding to amino acids 1-143, modified by PCR to include a FLAG epitope following amino acid 143, was subcloned into pSec-Tag2 HygroA (Invitrogen, Carlsbad, Calif.) and used for transfection of COSM6 cells as described (Perrin et al., 2001). After 4 days, the media was collected and sCRFR2α was enriched by purification using FLAG-agarose (Sigma, St. Louis, Mo.) immunoaffinity chromatography. The protein was detected by immunoblot analysis using either the anti-FLAG antibody or the antibody generated to the unique sCRFR2α C-terminus.
Bacterial expression of sCRFR2α: A cDNA corresponding to amino acids 20-143 was generated by PCR using mCRFR2α as the template. The cDNA was subcloned into pET-32a(+) (Novagen, La Jolla, Calif.) and the protein purified by S-protein affinity chromatography as described (Perrin et al., 2001). The protein was detected by immunoblot analysis using the antibody generated to the unique sCRFR2α C-terminus.
Radioreceptor assays. The soluble protein, purified either from COS M6 cell media or E. coli was incubated in triplicate wells with [¹²⁵I-DTyr^O]-astressin and increasing concentration of unlabeled peptides as described (Perrin et al., 2003).
B. Results
A cDNA transcript of smaller (˜100 bp) size was observed during the isolation of the mouse CRFR2α (Van Pett et al., 2000). This smaller fragment was isolated and found to encode a variant of CRFR2α bearing a deletion of exon six. Translation of the variant transcript predicts a novel 143 amino acid protein, sCRFR2α, comprising the majority of the first extracellular domain of CRFR2α followed by a unique 38 amino acid C terminus (FIG. 1A). Screening of GenBank showed homology of the C-terminus to no other protein. The genomic arrangement of the sCRFR2α is shown in FIG. 1B.
If the sCRFR2α mRNA is merely a product of splicing errors, it should be much less abundant than the correctly spliced RNA. In order to examine this question, semi- quantitative RT-PCR followed by Southern hybridization analysis was used to compare the relative abundance of CRFR2α and sCRFR2α mRNA in several brain regions. Total RNA prepared from mouse tissues was reverse-transcribed to generate cDNAs that were used as templates for semi-quantitative RT-PCR analysis, followed by Southern hybridization, using specific primers and probes for CRFR2α and sCRFR2α (FIG. 2). The oligonucleotide primer pair (located in exons three and seven) allowed the simultaneous amplification of both the soluble form and the full-length membrane bound receptor in a single reaction (FIG. 2A). The sCRFR2α is highly expressed in the olfactory, cortex, midbrain and the pituitary (FIGS. 2B and 2C). Lower levels of expression were found in the hippocampus, hypothalamus, pons, medulla and spinal cord (FIGS. 2B and 2C). As shown in FIG. 2, the abundance of sCRFR2α mRNA is lower, but comparable, to that of CRFR2α mRNA. The sequences of cDNA fragments from RT-PCR were found to encode a splice variant of the mouse CRFR2α gene (FIG. 1A).
Computer analysis of the sequence predicted that the first 19 amino acids serve as a putative signal peptide. Because the sequence contains no obvious sites for membrane attachment, the protein is hypothesized to be secreted as a soluble form. To explore this hypothesis, the protein was expressed in COS M6 cells. Following purification from the media, a protein band of ˜30 kD was visualized by immunoblot analyses using either anti-FLAG antiserum or the anti-sCRFR2α, an antiserum raised against a synthetic peptide fragment encoding the unique C-terminal tail of sCRFR2α protein (aa 113-143) (FIG. 3A). The larger size of the protein compared to that predicted from the cDNA is probably a result of glycosylation.
In order to obtain a larger quantity of sCRFR2α, a protein lacking the putative signal peptide was expressed as a fusion protein in E. coli (Perrin et al., 2001). Following cleavage and purification, the protein was visualized (using the anti-sCRFR2α) by immunoblot analysis as a narrow band of size ˜20 kD. The anti-sCRFR2α serum detects the sCRFR2α proteins both in radioimmunoassay (FIG. 3B) as well as in immonocytochemistry (FIG. 3C).
Immunohistochemical studies using anti-sCRFR2α serum revealed the distribution of sCRFR2α-ir in rodent brain. The cellular distribution of immunolabeling for sCRFR2α-ir was widespread and conformed more closely to the location of CRFR1 mRNA expression pattern than to that of CRFR2 (FIGS. 4A-4F). The results described are from studies in mice; a similar pattern of labeling was observed in rats. Major sites of cellular expression include mitral and tufted cells of the olfactory bulb, the medial septavdiagonal band complex, piriform cortex, substantia nigra, red nucleus, basolateral amygdaloid, deep cerebellar and dorsal column nuclei, all of which are prominent sites of CRFR1 expression. Similar to CRFR1, sCRFR2α-ir cell bodies are numerous throughout isocortex, although the laminar distributions are only partly overlapping. Thus, while both CRFR1- and sCRFR2α-expressing cell bodies are numerous in layer 2/3, the dominant cortical seat of CRFR1 expression is in layer 4, while that of sCRFR2α is in layer 5. Major sites of CRFR2 expression, including the lateral septal, midbrain raphe, ventromedial hypothalamic and medial amygdaloid nuclei were all lacking in sCRFR2α-stained cell bodies, although interestingly the latter two sites were among the few invested with labeled varicosities that the inventors take to be representative of sCRFR2α-ir terminal fields. The paraventricular nucleus of the hypothalamus also contained a presumed sCRFR2α-ir terminal field of moderate density.
Labeling throughout the brain was blocked by pre-incubation of the antiserum with low micromolar concentrations (≧30 μM) of the sCRFR2α (113-143) peptide used as immunogen; competition with the corresponding peptide predicted from the CRFR1 sequence did not interfere with immunolabeling at concentrations as high as 3 mM. Further support for the specificity of labeling are observations that all immunolocalizations persisted in CRFR1- and/or CRFR2-deleted mice; note that the targeting construct used for generating each of the existing receptor-knockout lines would be expected to spare the sCRFR2α coding region (Smith et al., 1998; Timpl et al., 1998; Bale et al., 2000).
In order to determine the presence of sCRFR2α-like ir in brain, a highly specific radioimmunoassay was developed using anti-sCRFR2α-and [¹²⁵I-Tyr¹¹³] sCRFR2α (113-143)] as the tracer. Tissue from mouse brain was acid-extracted, partially purified on C18 cartridges and assayed at multiple doses in the radioimmunoassay. The tissue extracts displaced [¹²⁵I-Tyr¹¹³] sCRFR2α (113-143)] bound to anti-sCRFR2α in a dose-dependent manner (FIG. 4G). Highest levels of expression were found in the olfactory bulb, hypothalamus, cortex and midbrain, all of which correlate with the presence of ir cells and fibers, determined by the immunohistochemical studies (FIG. 4). A putative soluble form of CRFR1 (generated by deletion of exon 5) would comprise a different unique C-terminal sequence. A protein corresponding to that sequence did not displace [¹²⁵I-Tyr¹¹³] sCRFR2α(113-143) in the radioimmunoassay. These results further confirm the existence of sCRFR2α protein in rodent CNS.

The interactions of the sCRFR2α with CRF family ligands were assessed by radioreceptor assay using competitive displacement of [¹²⁵I-D Tyr⁰]-astressin bound to sCRFR2α. The soluble proteins, secreted by COS M6 cells or produced in bacteria, bind the agonists, Ucn 1 and CRF, as well as the antagonist, astressin, with nanomolar affinities, whereas, the affinities for Ucn 2 and Ucn 3 are much lower (Table 2).

TABLE 2


Inhibitory binding constants, Ki (nM) for CRF ligands binding to sCRFR2αproteins.

Protein	CRF	rUcn1	mUcn2	mUcn3	Astressin

mam sCRFR2α	23 (14-39)	6.6 (3.5-12)	113 (68-190)	>200	6.7 (3.6-12)
bact sCRFR2α	14.8 (9.2-24)	5.8 (2.5-13.3)	116 (85-158)	>200	10 (7.9-12.5)

Binding of CRF family members to sCRFR2αproteins purified from either COS M6 cell media (mam sCRFR2α) or E. coli (bactsCRFR2α). See Methods for details.

To delineate the possible hnctions of sCRFR2α, the inventors studied its effects on signaling by CRF family ligands. Both the mammalian and bacterially expressed sCRFR2α proteins inhibit, in a dose dependent manner, the cAMP response to Ucn 1 and CRF in HEK293T cells transfected with mouse CRFR2α as measured by the CRE luciferase activity of the EVX1 gene (FIG. 5A). Because the urocortins activate MAPK signaling (Brar et al., 2002), the inventors measured the ability of sCRFR2α to inhibit the activation by Ucn 1 of ERK1/2-p42,44 in CATH.a cells, which endogenously express CRFR1 and CRFR2α. The sCRFR2α inhibits the induction of phosphorylated ERK by Ucn 1 in CATH.a cells (FIG. 5B).
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

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Claims

1. An isolated, soluble corticotropin releasing factor receptor type 2 (sCRFR2).

2. The sCRFR2 of claim 1, wherein the sCRFR2 comprises an amino terminal extracellular domain of a corticotropin releasing factor receptor type 2.

3. The sCRFR2 of claim 1, wherein the amino acid sequence of the sCRFR2 comprises an amino acid sequence encoded by exons 3, 4, and 5 of the CRFR2 gene.

4. The sCRFR2 of claim 1, wherein the sCRFR2 comprises an amino acid sequence of at least 50 amino acids that are at least 70% similar to the amino acid sequence of SEQ ID NO:4, SEQ ID NO:8, or SEQ ID NO: 12.

5. The sCRFR2 of claim 4, wherein the sCRFR2 comprises an amino acid sequence of at least 50 amino acids that are at least 90% similar to the amino acid sequence of SEQ ID NO:4, SEQ ID NO:8, or SEQ ID NO:12.

6. The sCRFR2 of claim 5, wherein the sCRFR2 comprises an amino acid sequence of at least 50 amino acids that are at least 95% similar to the amino acid sequence of SEQ ID NO:4, SEQ ID NO:8, or SEQ ID NO:12.

7. The sCRFR2 of claim 6, wherein the sCRFR2 comprises an amino acid sequence an amino acid sequence of at least 50 amino acids of SEQ ID NO:4, SEQ ID NO:8, or SEQ ID NO:12.

8. The sCRFR2 of claim 1, wherein the isolated sCRFR2 further comprises an affinity tag, a label, a radionuclide, an enzyme, a fluorescent marker, a chemiluminescent marker, an immunoglobulin domain or a combination thereof.

9. The sCRFR2 of claim 8, wherein the isolated sCRFR2 further comprises an affinity tag.

10. The sCRFR2 of claim 8, wherein the isolated sCRFR2 further comprises a fluorescent marker.

11. The sCRFR2 of claim 8, wherein the isolated sCRFR2 further comprises an immunoglobulin domain.

12. The sCRFR2 of claim 11, wherein the sCRFR2 comprises an immunoglobulin Fc domain.

13. The s sCRFR2 of claim 1, further comprising a leader sequence.

14. The sCRFR2 of claim 1, wherein the sCRFR2 is conjugated to a polymer.

15. The sCRFR2 of claim 14 wherein the polymer is polyethylene glycol (PEG).

16. An isolated nucleic acid encoding at least 50 consecutive amino acids of a sCRFR2.

17. The nucleic acid of claim 16, further comprising a promoter operably coupled to the nucleic acid encoding the sCRFR2.

18. The nucleic acid of claim 17, wherein the nucleic acid is an expression cassette.

19. The nucleic acid of claim 18, wherein the expression cassette is comprised in an expression vector.

20. The nucleic acid of claim 19, wherein the expression vector is a linear nucleic acid, a plasmid expression vector, or a viral expression vector.

21. The nucleic acid of claim 19, wherein the expression vector is operably coupled to a delivery vector.

22. The nucleic acid of claim 21, wherein the delivery vector is a liposome, a polypeptide, a polycation, a lipid, a bacterium, or a virus.

23. A method of modulating activity of a G-protein coupled receptor (GPCR) comprising administering an effective dose of a sCRFR2 to a subject in need thereof, wherein binding of a GPCR ligand to a cell surface GPCR is reduced.

24. The method of claim 23, where the ligand is corticotropin releasing factor (CRF), urocortin 1, urocortin 2, urocortin 3, or stresscopin.

25. The method of claim 23, wherein administering is by ingestion, injection, endoscopy, or perfusion.

26. The method of claim 25, wherein administering is by injection.

27. The method of claim 26, wherein injection is intravenous injection, intramuscular injection, subcutaneous injection, intradermal injection, intracranial injection or intraperitoneal injection.

28. The method of claim 23, wherein the subject is human.

29. The method of claim 23, further comprising treating a disorder resulting from hyperactivation of a GPCR or hypersecretion of GPCR ligand.

30. The method of claim 29, wherein the disorder is type II diabetes.

31. The method of claim 29, wherein the disorder is an type II diabetes, insulin sensitivity, anxiety-related disorders; a mood disorders; bipolar disorders; post-traumatic stress disorder; inflammatory disorders; chemical dependencies and addictions; gastrointestinal disorders; or skin disorders.

32. The method of claim 31, wherein the anxiety-related disorder is generalized anxiety or the mood disorder is depression.

33. The method of claim 31, wherein the gastrointestinal disorder is irratable bowel syndrome.